[horizon][stable] [release] Proposal to make stable/queen as EOL

Hi all, As discussed in the last horizon weekly meeting[1] on 2021-06-23, I would like to announce that the horizon team decided to make stable/queen branch as EOL. Consider this mail as an official announcement for that. I would like to know if anyone still would like to keep this branch to be open otherwise, I will purpose an EOL patch for this branch. Thanks & Regards, Vishal Manchanda [1] https://meetings.opendev.org/meetings/horizon/2021/horizon.2021-06-23-15.00....