Fix spelling of occurred

What does this MR do?

Fix occurrences of occurred being incorrectly spelled with only one r.

I noticed it was incorrectly spelled when creating https://gitlab.com/gitlab-org/gitlab-ce/issues/38357

Are there points in the code the reviewer needs to double check?

Spelling is correct. Tests still passing.

Why was this MR needed?

English spelling in application was incorrect.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the [merge request performance guides](https://docs.gitlab.com/ee/development/merge_request_performance_guidelines.html)
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?