[submodule] Update submodule linkmgrd to the latest HEAD automaticall…

…y (#20072)

#### Why I did it
src/linkmgrd
```
* d1b5dcc - (HEAD -> 202305, origin/202305) Fix default route race condition UT (Azure#258) (Azure#273) (12 hours ago) [Longxiang Lyu]
* 7411fb3 - Fix pipeline for 202305 swss common vstest failed. (Azure#275) (17 hours ago) [Liu Shilong]
```
#### How I did it
#### How to verify it
#### Description for the changelog