Release syntax aware heuristic expansion of diagnostic excerpts (#22858)

Implementation PR was #21942

Release Notes:

- Improved diagnostic excerpts by using syntactic info to determine the
context lines to show.

crates/diagnostics/Cargo.toml

@@ -18,7 +18,6 @@ collections.workspace = true
 ctor.workspace = true
 editor.workspace = true
 env_logger.workspace = true
-feature_flags.workspace = true
 gpui.workspace = true
 language.workspace = true
 log.workspace = true