[submodule] Update submodule sonic-restapi to the latest HEAD automatically (#19169)

#### Why I did it
src/sonic-restapi
```
* 4a564ba - (HEAD -> master, origin/master, origin/HEAD) Fix buster-backports debian mirror issue. (#152) (4 days ago) [Liu Shilong]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld