Fix typo on Design LFS enabling notice

What does this MR do?

This MR fixes a typo in the notice displayed above the Design Management section of an issue when a project does not have LFS enabled.

The copy previously said "[...] you'll need to enable LFS and have admin enable hashed storage" and that has been corrected to "have an admin".

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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