[submodule] Update submodule sonic-sairedis to the latest HEAD automatically (sonic-net#18303)

#### Why I did it
src/sonic-sairedis
```
* bb948f6 - (HEAD -> master, origin/master, origin/HEAD) Check MDIO server thread joinable before join the thread (sonic-net#1342) (18 hours ago) [Jiahua Wang]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld