Reword "Internal Changes" description

The "Internal Changes" section currently says "no direct user facing
benefits", but includes "significant improvements to the ... overall
performance", which is a user-facing benefit. Reword it to say "do not
affect any public interfaces" instead.

Author: joshtriplett

RELEASES.md

@@ -92,9 +92,9 @@ Compatibility Notes
 Internal Changes
 ----------------
 
-These changes provide no direct user facing benefits, but represent significant
-improvements to the internals and overall performance of rustc
-and related tools.
+These changes do not affect any public interfaces of Rust, but they represent
+significant improvements to the performance or internals of rustc and related
+tools.
 
 - Windows builds now use profile-guided optimization, providing 10-20% improvements to compiler performance: [Utilize PGO for windows x64 rustc dist builds](https://github.com/rust-lang/rust/pull/96978/)
 - [Stop keeping metadata in memory before writing it to disk](https://github.com/rust-lang/rust/pull/96544/)