Drop Einsum.index_to_access_descr?

[inducer]

@nkoskelo pointed out that there does not seem to be a strong rationale for keeping that attribute around. Should we get rid of it?

cc @kaushikcfd

[kaushikcfd]

We had just kept that to make it easier for user to tag the axes of an einsum which is only good for demonstration purposes. I wouldn't mind scraping it.

[inducer]

@nkoskelo I'd be open to a patch removing it.