[submodule] Update submodule sonic-snmpagent to the latest HEAD automatically (#22502)

#### Why I did it
src/sonic-snmpagent
```
* f55bee8 - (HEAD -> master, origin/master, origin/HEAD) snmpagent: modify entities to include fans under fabric module (#349) (10 hours ago) [Mohan Yelugoti]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld