Fix typo of GitLab Pages in admin UI

What does this MR do?

Fixes typo of GitLab Pages in admin UI, which is a regression regression:12.2 due to gitlab-foss!29306 (merged).

cf. after gitlab-foss!29306 (merged), there were !18666 (merged) and !14797 (merged), but either of them did not fix it.

before	after

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because tiny UI text on admin dashboard relevant to Category:Internationalization.
• Code review guidelines
• Style guides
• Separation of EE specific content