[submodule] Update submodule sonic-gnmi to the latest HEAD automatica…

…lly (#20516)

#### Why I did it
src/sonic-gnmi
```
* 743c7af - (HEAD -> master, origin/master, origin/HEAD) Update dbus timeout (#305) (26 hours ago) [ganglv]
* 470e275 - Use version of gocov supported by sonic-gnmi (#300) (2 days ago) [Zain Budhwani]
```
#### How I did it
#### How to verify it
#### Description for the changelog