[functorch] Remove internal assert in index_put batch rule (#100516)
Fixes #94630
Context: https://github.com/pytorch/pytorch/issues/94630#issuecomment-1518946929
I'm not sure how to correctly test it using pure `vmap` without joining `jacrev` here.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100516
Approved by: https://github.com/zou3519
