docs: consistently describe default features

Consistently describe te default features, include that *ring* is
default enabled.

rustls/src/lib.rs

@@ -242,28 +242,26 @@
 //! Here's a list of what features are exposed by the rustls crate and what
 //! they mean.
 //!
-//! - `logging`: this makes the rustls crate depend on the `log` crate.
-//!   rustls outputs interesting protocol-level messages at `trace!` and `debug!`
-//!   level, and protocol-level errors at `warn!` and `error!` level.  The log
-//!   messages do not contain secret key data, and so are safe to archive without
-//!   affecting session security.  This feature is in the default set.
-//!
-//! - `tls12`: enables support for TLS version 1.2. This feature is in the default
-//!   set. Note that, due to the additive nature of Cargo features and because it
-//!   is enabled by default, other crates in your dependency graph could re-enable
-//!   it for your application. If you want to disable TLS 1.2 for security reasons,
-//!   consider explicitly enabling TLS 1.3 only in the config builder API.
-//!
-//! - `read_buf`: When building with Rust Nightly, adds support for the unstable
+//! - `logging` (enabled by default): make the rustls crate depend on the `log` crate.
+//!   rustls outputs interesting protocol-level messages at `trace!` and `debug!` level,
+//!   and protocol-level errors at `warn!` and `error!` level.  The log messages do not
+//!   contain secret key data, and so are safe to archive without affecting session security.
+//!
+//! - `tls12` (enabled by default): enable support for TLS version 1.2. Note that, due to the
+//!   additive nature of Cargo features and because it is enabled by default, other crates
+//!   in your dependency graph could re-enable it for your application. If you want to disable
+//!   TLS 1.2 for security reasons, consider explicitly enabling TLS 1.3 only in the config
+//!   builder API.
+//!
+//! - `read_buf`: when building with Rust Nightly, adds support for the unstable
 //!   `std::io::ReadBuf` and related APIs. This reduces costs from initializing
 //!   buffers. Will do nothing on non-Nightly releases.
 //!
-//! - `ring`: this makes the rustls crate depend on the *ring* crate,
-//!   which is used for cryptography by default
-//!   Without this feature, these items must be provided externally to the core
-//!   rustls crate: see [`crate::crypto::CryptoProvider`].
+//! - `ring` (enabled by default): makes the rustls crate depend on the *ring* crate, which is
+//!    used for cryptography by default. Without this feature, these items must be provided
+//!    externally to the core rustls crate: see [`crate::crypto::CryptoProvider`].
 //!
-//! - `aws_lc_rs`: this makes the rustls crate depend on the aws-lc-rs crate,
+//! - `aws_lc_rs`: makes the rustls crate depend on the aws-lc-rs crate,
 //!   which can be used for cryptography as an alternative to *ring*.
 //!   Use `rustls::crypto::aws_lc_rs::default_provider()` as a `CryptoProvider`
 //!   when making a `ClientConfig` or `ServerConfig` to use aws-lc-rs