[neutron][networking-ovn] Propose to EOL stable/queens, stable/rocky and stable/stein branches of networking-ovn

Hi, The Queens, Rocky and Stein branches of networking-ovn see little activity and maintaining them and keeping their jobs running is a big effort. We discussed this topic during the team meeting (see [1]), and agreed to propose stable/queens, stable/rocky and stable/stein branches of networking-ovn End Of Life. I will wait until the end of next week for anyone who would like to step up as maintainer of those branches and who would at least try to fix CI of them. If there will be no volunteers for that, I will EOL those branches in networking-ovn. [1]: https://meetings.opendev.org/meetings/networking/2022/networking.2022-05-31-... Lajos Katona (lajoskatona)