Add spec/frontend/ to frontend roulette

What does this MR do?

Assign changes in spec/frontend/ to frontend developers in reviewer roulette.

Changelog entry added, if necessary
Documentation created/updated via this MR
Documentation reviewed by technical writer or follow-up review issue created
Tests added for this feature/bug
Tested in all supported browsers
Conforms to the code review guidelines
Conforms to the merge request performance guidelines
Conforms to the style guides
Conforms to the database guides
Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
Security reports checked/validated by reviewer

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