Fix Inaccurate documentation on ProfileFileCredentialsProvider

This commit addresses awslabs/aws-sdk-rust#746.

aws/rust-runtime/aws-config/src/profile/credentials.rs

@@ -61,9 +61,8 @@ impl ProvideCredentials for ProfileFileCredentialsProvider {
 /// let provider = ProfileFileCredentialsProvider::builder().build();
 /// ```
 ///
-/// _Note: Profile providers to not implement any caching. They will reload and reparse the profile
-/// from the file system when called. See [CredentialsCache](aws_credential_types::cache::CredentialsCache) for
-/// more information about caching._
+/// _Note: Profile providers, when called, will load and parse the profile from the file system
+/// only once. Parsed file contents will be cached indefinitely._
 ///
 /// This provider supports several different credentials formats:
 /// ### Credentials defined explicitly within the file