[submodule] Update submodule linkmgrd to the latest HEAD automatically (#17435)

#### Why I did it
src/linkmgrd
```
* e420df4 - (HEAD -> master, origin/master, origin/HEAD) Exclude DbInterface in PR coverage check (#224) (5 hours ago) [Jing Zhang]
```
#### How I did it
#### How to verify it
#### Description for the changelog
This commit is contained in:
mssonicbld 2023-12-07 16:34:16 +08:00 committed by GitHub
parent 719e41bab4
commit 28a7f20062
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23

@ -1 +1 @@
Subproject commit 489f6cee955a10d5d6d576d8258e1bd69efa5665
Subproject commit e420df41a08ea9ec421687fb06d1f96535ebf151