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

…lly (sonic-net#19896)

#### Why I did it
src/sonic-gnmi
```
* 64ed32b - (HEAD -> master, origin/master, origin/HEAD) Merge pull request sonic-net#274 from isabelmsft/file_stat_gnoi (5 days ago) [isabelmsft]
* 46df786 - fix spacing (8 days ago) [isabelmsft]
* 894ffe6 - fix spacing (8 days ago) [isabelmsft]
* 6fe7d32 - fix formatting (8 days ago) [isabelmsft]
* 6b435c9 - uncomment check (2 weeks ago) [isabelmsft]
* 302ca17 - increase coverage (2 weeks ago) [isabelmsft]
* 0b2cb90 - fix local test (2 weeks ago) [isabelmsft]
* 7c392c8 - fix syntax (2 weeks ago) [isabelmsft]
* e06641d - inc cov atmpt (2 weeks ago) [isabelmsft]
* 328e631 - Merge branch 'file_stat_gnoi' of https://github.com/isabelmsft/sonic-gnmi into file_stat_gnoi (3 weeks ago) [isabelmsft]
|\ 
| failure_prs.log 8944bb1 - Merge branch 'master' into file_stat_gnoi (3 weeks ago) [isabelmsft]
* | 14bf34a - update test (3 weeks ago) [isabelmsft]
|/ 
* ad0e226 - add UT, clean error (3 weeks ago) [isabelmsft]
* 34a94d6 - update (3 weeks ago) [isabelmsft]
* d860f28 - update file system (3 weeks ago) [isabelmsft]
* 36ec608 - update (3 weeks ago) [isabelmsft]
* 3430dd2 - update (3 weeks ago) [isabelmsft]
* 0b70222 - update (3 weeks ago) [isabelmsft]
* 5236768 - update (3 weeks ago) [isabelmsft]
* 0fe0971 - feature change (3 weeks ago) [isabelmsft]
```
#### How I did it
#### How to verify it
#### Description for the changelog