[submodule] Update submodule sonic-ztp to the latest HEAD automatical…

…ly (sonic-net#19630)

#### Why I did it
src/sonic-ztp
```
* b4cdd8c - (HEAD -> master, origin/master, origin/HEAD) Add role field to the ztp PORT config (sonic-net#57) (24 hours ago) [Vivek]
```
#### How I did it
#### How to verify it
#### Description for the changelog