Fix snippet bug when geo primary is enabled

What does this MR do?

This MR fixes two problems:

• The first one is in EE when Gitlab::Geo.primary?. We call identifier_for_container passing the project but, that's not right, it must be container. (PersonalSnippet does not have a project so this will raise an error.
• Geo should not perform (at the moment) any action for snippet repositories. Therefore we only allow this when repo_type.project?.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content