can the master branch be removed (now that default is main)?

[thaJeztah]

This repository renamed the default branch to main, but it looks like there's an old master branch still present; muscle memory makes me pick the wrong branch as "upstream", and get me tricked each time 😂

As far as I can see, the branch has no commits that are not in main (behind, no "ahead"), so can probably be removed without a need to archive it.

☝️ I also did a quick check of all open pull requests, and all of them are targeting the correct (main) branch, so removing the branch should not impact current PRs.

[thaJeztah]

cc @aboch

[aboch]

cc @vishvananda