[snmpagent] Update submodule pointer for snmpagent (#6850)

183162f Fix issue: expect redis pubsub data to be str type instead of bytes type (#196)

#### Why I did it

Update submodule pointer for snmpagent to include PR sonic-net/sonic-snmpagent#196 

#### How I did it

Update submodule pointer for snmpagent

#### How to verify it

Run build