Container registry return 403 instead of 500 for permission errors

What does this MR do and why?

In https://gitlab.com/gitlab-com/request-for-help/-/issues/2943#note_2544621665

we realized that we are returning a 500 for something that should really be a 403, namely permission related issues.

This MR aims to check for the type of an error when returned and properly return a 403.

References

Closes #547910

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