chore: Replace as_any functions with trait upcasting (#28221)

Closes #ISSUE

Release Notes:

- N/A

crates/language/src/buffer.rs

@@ -306,7 +306,7 @@ pub enum BufferEvent {
 }
 
 /// The file associated with a buffer.
-pub trait File: Send + Sync {
+pub trait File: Send + Sync + Any {
     /// Returns the [`LocalFile`] associated with this file, if the
     /// file is local.
     fn as_local(&self) -> Option<&dyn LocalFile>;
@@ -336,9 +336,6 @@ pub trait File: Send + Sync {
     /// This is needed for looking up project-specific settings.
     fn worktree_id(&self, cx: &App) -> WorktreeId;
 
-    /// Converts this file into an [`Any`] trait object.
-    fn as_any(&self) -> &dyn Any;
-
     /// Converts this file into a protobuf message.
     fn to_proto(&self, cx: &App) -> rpc::proto::File;
 
@@ -4610,10 +4607,6 @@ impl File for TestFile {
         WorktreeId::from_usize(0)
     }
 
-    fn as_any(&self) -> &dyn std::any::Any {
-        unimplemented!()
-    }
-
     fn to_proto(&self, _: &App) -> rpc::proto::File {
         unimplemented!()
     }