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

Closes #ISSUE

Release Notes:

- N/A

crates/copilot/src/copilot.rs

@@ -1280,10 +1280,6 @@ mod tests {
             unimplemented!()
         }
 
-        fn as_any(&self) -> &dyn std::any::Any {
-            unimplemented!()
-        }
-
         fn to_proto(&self, _: &App) -> rpc::proto::File {
             unimplemented!()
         }