Revert "chore: Bump Rust version to 1.77 (#9631)" (#9658)

This reverts commit 6184278faf.

We can't upgrade to Rust 1.77 until there are Rust 1.77 Docker images
available
(https://github.com/docker-library/official-images/pull/16457).


Release Notes:

- N/A

crates/language/src/language_registry.rs

@@ -80,11 +80,8 @@ struct AvailableLanguage {
 
 enum AvailableGrammar {
     Native(tree_sitter::Language),
-    Loaded(#[allow(unused)] PathBuf, tree_sitter::Language),
-    Loading(
-        #[allow(unused)] PathBuf,
-        Vec<oneshot::Sender<Result<tree_sitter::Language>>>,
-    ),
+    Loaded(#[allow(dead_code)] PathBuf, tree_sitter::Language),
+    Loading(PathBuf, Vec<oneshot::Sender<Result<tree_sitter::Language>>>),
     Unloaded(PathBuf),
 }