remove unused PayloadAction import

Author: ben.durrant

docs/api/createSlice.mdx

@@ -142,7 +142,6 @@ The main benefit of this is that you can create [async thunks](./createAsyncThun
 
 ```ts title="Creator callback for reducers"
 import { createSlice, nanoid } from '@reduxjs/toolkit'
-import type { PayloadAction } from '@reduxjs/toolkit'
 
 interface Item {
   id: string