[submodule] Update submodule sonic-gnmi to the latest HEAD automatically (#18387)

#### Why I did it
src/sonic-gnmi
```
* 3fa77c6 - (HEAD -> master, origin/master, origin/HEAD) Support multiple database for DPU (#188) (20 hours ago) [ganglv]
```
#### How I did it
#### How to verify it
#### Description for the changelog
This commit is contained in:
mssonicbld 2024-03-19 19:00:48 +08:00 committed by GitHub
parent f1439ee6c5
commit b1b79c5c94
No known key found for this signature in database
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@ -1 +1 @@
Subproject commit d56712a085a258a214917fac00db8d9383e9fb96
Subproject commit 3fa77c6148d7b9c9d00d5d6142fa05effdbecfcc