`cross-fetch` can be removed from the dependece list

[imsys]

cross-fetch was replaced by eth-json-rpc-middleware/fetch at the commit eeefd6f , the older version of cross-fetch has a vulnerability and package managers will be complaining about it. It can be removed without problems.

[brianlenz]

What's the hold-up on #404 here? Seems like a pretty straight-forward PR to merge. I audited the code on main branch and can confirm cross-fetch is no longer used and is safe to remove.