[submodule] Update submodule sonic-snmpagent to the latest HEAD automatically (sonic-net#21913)

#### Why I did it
src/sonic-snmpagent
```
* 25f9e4f - (HEAD -> master, origin/master, origin/HEAD) Handle error seen when interface counter is not available in COUNTERS_DB (sonic-net#341) (25 hours ago) [SuvarnaMeenakshi]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld