Change example custom Container Registry port to 5010

What does this MR do?

This changes the example port number change in our Container Registry configuration guide, from 5001 to 5010.

The main reason to change this port is to fix a conflict with other software installed together with the container registry of GitLab, on the same computer. For example, we've seen that data-dog uses 5000, and 5001. The change makes the example code work in the case of an administrator who just copy/pastes the code snippets when following the guide: we can set them up for success instead of a second collision which we already know about.

This also avoids conflicting with the GitLab Registry debug server further down the page, which uses 5001 as well.

Related issues

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