Docs(GitLab): add entrypoint for distroless image (#9093)
## Summary
Update the docs for the GitLab integration, to make it clear that an
entrypoint has to be specified, when a distroless image is being used.
## Test Plan
Without specifying an entrypoint when using a distroless image:
<img
src=https://github.com/user-attachments/assets/35499bd5-51d8-4016-b1d0-2d56956f82e6
width=500>
_It works if you either specify the entrypoint or if the image used in
not a distroless one._
Co-authored-by: Tsafaras <konstantinos@valuechecker.ai>
