Remove Immer ES5 legacy compat

packages/toolkit/src/index.ts

@@ -1,4 +1,3 @@
-import { enableES5 } from 'immer'
 export * from 'redux'
 export {
  default as createNextState,
@@ -18,12 +17,6 @@ export type {
 export { createDraftSafeSelector } from './createDraftSafeSelector'
 export type { ThunkAction, ThunkDispatch, ThunkMiddleware } from 'redux-thunk'
 
-// We deliberately enable Immer's ES5 support, on the grounds that
-// we assume RTK will be used with React Native and other Proxy-less
-// environments. In addition, that's how Immer 4 behaved, and since
-// we want to ship this in an RTK minor, we should keep the same behavior.
-enableES5()
-
 export {
  // js
  configureStore,