Apply suggestion from @maartenba

Author: maartenba

src/content/docs/identityserver/tokens/client-authentication.md

@@ -476,7 +476,7 @@ var idsvrBuilder = builder.Services.AddIdentityServer(options =>
 
 Specifying this domain name however triggers an additional authentication step in the [MutualTlsEndpointMiddleware][1], 
 calling `httpContext.AuthenticateAsync()` with the configured client certificate authentication scheme name.
-By default, this scheme name is `"Certificate"`, but you can override this when configuring the MTLS options:
+By default, this scheme name is `"Certificate"`, but you can override this when configuring the mTLS options:
 
 ```csharp {6}
 // Program.cs