docs: remove redundant doc comments about feature reqs

Now that we've enabled `doc_auto_cfg` these comments are redundant with
the auto-generated `docs.rs` notes about required features.

src/crl.rs

@@ -76,8 +76,6 @@ impl CertificateRevocationList {
 	}
 	/// Serializes the certificate revocation list (CRL) in ASCII PEM format, signed with
 	/// the issuing certificate authority's key.
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_pem_with_signer(&self, ca: &Certificate) -> Result<String, RcgenError> {
 		let contents = self.serialize_der_with_signer(ca)?;

src/csr.rs

@@ -98,8 +98,6 @@ impl CertificateSigningRequest {
 		self.params.serialize_der_with_signer(&self.public_key, ca)
 	}
 	/// Serializes the requested certificate, signed with another certificate's key, to the ASCII PEM format
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_pem_with_signer(&self, ca: &Certificate) -> Result<String, RcgenError> {
 		let contents = self

src/error.rs

@@ -35,8 +35,6 @@ pub enum RcgenError {
 	Time,
 	#[cfg(feature = "pem")]
 	/// Error from the pem crate
-	///
-	/// *This variant is only available if rcgen is built with the "pem" feature*
 	PemError(pem::PemError),
 	/// Error generated by a remote key operation
 	RemoteKeyError,

src/key_pair.rs

@@ -57,8 +57,6 @@ impl KeyPair {
 		Ok(der.try_into()?)
 	}
 	/// Parses the key pair from the ASCII PEM format
-	///
-	/// *This constructor is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn from_pem(pem_str: &str) -> Result<Self, RcgenError> {
 		let private_key = pem::parse(pem_str)?;
@@ -79,8 +77,6 @@ impl KeyPair {
 	/// using the specified [`SignatureAlgorithm`]
 	///
 	/// Same as [from_pem_and_sign_algo](Self::from_pem_and_sign_algo).
-	///
-	/// *This constructor is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn from_pem_and_sign_algo(
 		pem_str: &str,
@@ -296,8 +292,6 @@ impl KeyPair {
 	/// Return the key pair's public key in PEM format
 	///
 	/// The returned string can be interpreted with `openssl pkey --inform PEM -pubout -pubin -text`
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn public_key_pem(&self) -> String {
 		let contents = self.public_key_der();
@@ -337,8 +331,6 @@ impl KeyPair {
 	}
 
 	/// Serializes the key pair (including the private key) in PKCS#8 format in PEM
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_pem(&self) -> String {
 		let contents = self.serialize_der();

src/lib.rs

@@ -564,8 +564,6 @@ impl CertificateParams {
 	/// Parses a ca certificate from the ASCII PEM format for signing
 	///
 	/// See [`from_ca_cert_der`](Self::from_ca_cert_der) for more details.
-	///
-	/// *This constructor is only available if rcgen is built with the "pem" and "x509-parser" features*
 	#[cfg(all(feature = "pem", feature = "x509-parser"))]
 	pub fn from_ca_cert_pem(pem_str: &str, key_pair: KeyPair) -> Result<Self, RcgenError> {
 		let certificate = pem::parse(pem_str).or(Err(RcgenError::CouldNotParseCertificate))?;
@@ -585,8 +583,6 @@ impl CertificateParams {
 	/// and left to defaults.
 	///
 	/// Will not check if certificate is a ca certificate!
-	///
-	/// *This constructor is only available if rcgen is built with the "x509-parser" feature*
 	#[cfg(feature = "x509-parser")]
 	pub fn from_ca_cert_der(ca_cert: &[u8], key_pair: KeyPair) -> Result<Self, RcgenError> {
 		let (_remainder, x509) = x509_parser::parse_x509_certificate(ca_cert)
@@ -1566,26 +1562,20 @@ impl Certificate {
 		&self.key_pair
 	}
 	/// Serializes the certificate to the ASCII PEM format
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_pem(&self) -> Result<String, RcgenError> {
 		let contents = self.serialize_der()?;
 		let p = Pem::new("CERTIFICATE", contents);
 		Ok(pem::encode_config(&p, ENCODE_CONFIG))
 	}
 	/// Serializes the certificate, signed with another certificate's key, to the ASCII PEM format
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_pem_with_signer(&self, ca: &Certificate) -> Result<String, RcgenError> {
 		let contents = self.serialize_der_with_signer(ca)?;
 		let p = Pem::new("CERTIFICATE", contents);
 		Ok(pem::encode_config(&p, ENCODE_CONFIG))
 	}
 	/// Serializes the certificate signing request to the ASCII PEM format
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_request_pem(&self) -> Result<String, RcgenError> {
 		let contents = self.serialize_request_der()?;
@@ -1601,8 +1591,6 @@ impl Certificate {
 	/// Serializes the private key in PEM format
 	///
 	/// Panics if called on a remote key pair.
-	///
-	/// *This function is only available if rcgen is built with the "pem" feature*
 	#[cfg(feature = "pem")]
 	pub fn serialize_private_key_pem(&self) -> String {
 		self.key_pair.serialize_pem()