Fix CI failure

[taiki-e]

It appears type inferences no longer works due to the addition of several PartialEq implementations around CStr.

https://github.com/bytecodealliance/rustix/actions/runs/17935800005/job/51001634461

error[E0283]: type annotations needed
  --> tests/net/addr.rs:34:20
   |
34 |         cstr!("/").into()
   |                    ^^^^ cannot infer type for type parameter `U`
   |
   = note: cannot satisfy `_: From<&CStr>`
   = note: required for `&CStr` to implement `Into<_>`

error[E0283]: type annotations needed
  --> tests/path/arg.rs:19:32
   |
19 |     assert_eq!(cstr!("hello"), Borrow::borrow(&t.as_cow_c_str().unwrap()));
   |                                ^^^^^^^^^^^^^^ -------------------------- type must be known at this point
   |                                |
   |                                cannot infer type of the type parameter `Borrowed` declared on the trait `Borrow`
   |
   = note: multiple `impl`s satisfying `Cow<'_, CStr>: Borrow<_>` found in the following crates: `alloc`, `core`:
           - impl<'a, B> Borrow<B> for Cow<'a, B>
             where B: ToOwned, B: ?Sized;
           - impl<T> Borrow<T> for T
             where T: ?Sized;
help: consider specifying the generic argument
   |
19 |     assert_eq!(cstr!("hello"), Borrow::<Borrowed>::borrow(&t.as_cow_c_str().unwrap()));
   |                                      ++++++++++++