[submodule] Update submodule sonic-utilities to the latest HEAD autom…

…atically (#15812)

#### Why I did it
src/sonic-utilities
```
* 51c7a43c - (HEAD -> master, origin/master, origin/HEAD) [show][muxcable] update `show mux config` to print out `soc_ipv6` as well  (#2909) (6 hours ago) [Jing Zhang]
* fd497755 - [route_check][dualtor] Ignore vlan neighbor route miss (#2888) (18 hours ago) [Longxiang Lyu]
* 81c0ed4e - [show][muxcable] update `show mux tunnel-route` to check soc_ipv6 as well (33 hours ago) [Jing Zhang]
* 1ee73668 - [db_migrator] Migrate DNS configuratuion (#2893) (2 days ago) [ganglv]
* 553a3432 - [dualtor][route_check] filter out `soc_ipv6`  (#2899) (2 days ago) [Jing Zhang]
```
#### How I did it
#### How to verify it
#### Description for the changelog