Fix anchor link in UI

What does this MR do?

While following a link embedded in the UI, I noticed a bug in the anchor provided for the link.

Link now points to: https://gitlab.com/help/user/group/index.md#group-file-templates-premium.

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