remove redundant typed StorageImpl::data() member (#97650)
This has the same implementation as the unsafe variants and the unsafe
variants match the original semantics of the code, given that they
don't check that the type matches.
Given that we're updating callsites anyways to address the mutability
aspect, we might as well just drop this method now.
Differential Revision: [D44410210](https://our.internmc.facebook.com/intern/diff/D44410210/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/97650
Approved by: https://github.com/ezyang
