Add group file template tests

What does this MR do?

Adds e2e tests for group file templates.

gitlab-org/quality/testcases#114 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content