Don't hop on background queue to run onExit

Since we use Swift Concurrency now, we no longer need to be worried about queues blocking each other, so the queue hopping is no longer necessary.

Author: ahoppen

Sources/SourceKitLSP/SourceKitServer.swift

@@ -967,11 +967,7 @@ extension SourceKitServer {
     await prepareForExit()
 
     // Call onExit only once, and hop off queue to allow the handler to call us back.
-    let onExit = self.onExit
-    self.onExit = {}
-    DispatchQueue.global().async {
-      onExit()
-    }
+    self.onExit()
   }
 
   // MARK: - Text synchronization