fix(nvim): remove unused mut variables

nvim-core/src/lib.rs

@@ -194,7 +194,7 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
     }
 
     if should_kill_headless {
-        let mut child_to_kill = {
+        let child_to_kill = {
             let mut proc_lock = HEADLESS_PROC.lock().unwrap_or_else(|e| e.into_inner());
             proc_lock.take()
         };