[submodule] Update submodule sonic-gnmi to the latest HEAD automatically (#17436)

#### Why I did it
src/sonic-gnmi
```
* 88e82d4 - (HEAD -> master, origin/master, origin/HEAD) Replace PFC_WD_TABLE with PFC_WD (#173) (8 days ago) [Zain Budhwani]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld