task: remove the large pre-trained files from the repo history

[joanise]

Once #6 and EveryVoiceTTS/EveryVoice#807 are merged

Specifically, we want to remove the *.t7 and *.pth files in styletts2/pretrained/* from the history using git-filter-repo.

• filter the styletts2 repo

• rewrite the everyvoice history too, so that commits referring to the styletts2 submodules can still be checked out -- caveat: styletts2 won't run in those commits, since it'll be looking for files that don't exist

• Q: do we need to rename our fork to something else and create a fresh repo?

  • if cloning becomes small, this may not be necessary
  • if cloning after filtering still gets the large files, then definitely