Delete `production` branch

[Per Tillisch]

This can't be done via pull request, so I'll open an issue to host the proposal, discussion, and ruling.

The repository's production branch has historically served two purposes:

• Host the Library Manager index source list
• A "release branch"

Since the list will now be stored in arduino/library-registry, the first purpose is now obsolete, so the question of the second purpose remains. I would suggest switching to using tags for versioning, reconfiguring the indexer job to check out the latest tag. That does not exclude the use of release branches, but I don't feel that this project has any need for that strategy.

[Silvano Cerza]

Yeah, I think using tags would be the best approach. Something like we do in the CLI repo I guess.

[Roberto Sora]

Approved

[Per Tillisch]

Done. Thanks for the input!