Fix an issue that caused a precondition to be hit when an unknown request was sent to sourcekit-lsp

When sending an unknonw request to sourcekit-lsp, we directly called back `reply` and never set `replied` to `true` on the `RequestAndReply` object. This caused a preconditon to be hit when the `RequestAndReply` object got destroyed.

Author: ahoppen

Sources/SourceKitLSP/SourceKitServer.swift

@@ -921,7 +921,7 @@ extension SourceKitServer: MessageHandler {
       await self.handleRequest(for: request, requestHandler: self.prepareRename)
     // IMPORTANT: When adding a new entry to this switch, also add it to the `TaskMetadata` initializer.
     default:
-      reply(.failure(ResponseError.methodNotFound(R.method)))
+      await request.reply { throw ResponseError.methodNotFound(R.method) }
     }
   }
 }