doc: drop doc of 009_BA + add Florencenet

Merged as part of !2721 (merged)

Context

The Florence protocol variant with baking accounts has been rejected in favor of the variant without baking accounts. Consequently:

• the documentation still mentions protocol 009 with baking accounts: those pages should be removed to only keep the pages about 009 without baking accounts.
• the Florencenet network has been shut down, and the Florencenobanet network (i.e. the one without baking accounts) will be renamed into Florencenet. Since there were no releases with those names, we chose to only keep one simple name. Hence, the Test Networks page of the doc should also be updated to add Florencenet.

Manually testing the MR

Reviewers and approvers can test this MR by checking that the 009_BA doc no longer exists (including the protocol release page), and that the Florencenet is documented under Test Networks.

Checklist

• Select suitable reviewers using the Reviewers field below.