Remove useless import.

src/modules/websocket/slice.ts

@@ -1,5 +1,5 @@
 import { createAction, createSlice, PayloadAction } from '@reduxjs/toolkit';
-import { RootState, AppThunk } from '../../app/store';
+import { RootState } from '../../app/store';
 
 export enum SocketState {
   Opening,