[submodule] Update submodule linkmgrd to the latest HEAD automatically (#20012)

#### Why I did it
src/linkmgrd
```
* ff0cc80 - (HEAD -> 202311, origin/202311) [active-standby] Fix the oscillation logic (#261) (16 hours ago) [Longxiang Lyu]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld