[submodule] Update submodule sonic-gnmi to the latest HEAD automatically (sonic-net#24597)

#### Why I did it
src/sonic-gnmi
```
* 7938e3d - (HEAD -> master, origin/master, origin/HEAD) Use Go native file removal in gnoi_file.go, with remove.go file (sonic-net#522) (2 days ago) [ravaliyel]
* ad0da5b - gNOI: Add service client for Healthz Get RPC (sonic-net#486) (2 days ago) [jayaragini-hcl]
* fb17e28 - gNOI: Implement Healthz Client (sonic-net#485) (2 days ago) [jayaragini-hcl]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld