[submodule][202503] Update submodule sonic-sairedis to the latest HEAD automatically (sonic-net#1573)

#### Why I did it
src/sonic-sairedis
```
* 6fcbab6b - (HEAD -> 202503, origin/202503) Merge pull request sonic-net#86 from mssonicbld/sonicbld/202503-merge (16 hours ago) [mssonicbld]
* eacbd6c6 - Merge branch '202412' of https://github.com/Azure/sonic-sairedis.msft into 202503 (16 hours ago) [Sonic Automation]
* 550b66d6 - (origin/HEAD, origin/202412, 202412) Explicitly initialize default bulk chunk size in base counter context class (sonic-net#85) (27 hours ago) [Stephen Sun]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld