[submodule] Update submodule linkmgrd to the latest HEAD automatically (

#19458)

#### Why I did it
src/linkmgrd
```
* 6fcab47 - (HEAD -> master, origin/master, origin/HEAD) [active-standby] raising log level to notice for timed oscillation config change (#262) (28 hours ago) [Jing Zhang]
* 2b7e4f9 - [active-standby] Fix the oscillation logic (#261) (11 days ago) [Longxiang Lyu]
```
#### How I did it
#### How to verify it
#### Description for the changelog