[submodule] Update submodule dhcprelay to the latest HEAD automatically (#21159)

#### Why I did it
src/dhcprelay
```
* 2a2fb68 - (HEAD -> master, origin/master, origin/HEAD) Clear counter when dhcp6relay init (#51) (2 hours ago) [Yaqiang Zhu]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld