fix: delete-many keep selected items

[g3offrey]

Hi and happy new year to you 😄

I'm opening this pull request as I encountered a bug.
When I'm selecting rows in <List> and using the default "bulk delete" button, the rows disappear but the "header" still show "X item selected", until I refresh the page.

I investigated and found the issue.
It seems this code is not working as we are passing an array to indexOf.

const index = previousState.indexOf(action.payload.ids);	
if (index === -1) {	
  return previousState;	
}

I deleted it as this test seems useless in DELETE_MANY case.

Hope this is good ! 👌
Don't hesitate to tell me if I can do something more with this PR.

[djhi]

Thanks!