[kuryr] Propose to EOL stable branches (Stein, Rocky and Queens) for all the kuryr scope

Hello, We have plenty of stable branches in Kuryr repositories still open with the oldest being stable/queens. We haven't seen many backports[0] proposed to Stein, Rocky and Queens, so I would like to propose retiring these branches. Let me know if anybody is interested in keeping any of those branches. [0] https://review.opendev.org/q/(project:%255Eopenstack/kuryr.*)AND((branch:sta...)) Thank you, Maysa Macedo.