Fix delegate predicate method offences in metadatable

What does this MR do and why?

Remove delegate predicate method offence in ee/app/models/concerns/ee/ci/metadatable.rb.

Contributes to #324629 (closed)

How to set up and validate locally

REVEAL_RUBOCOP_TODO=1 bundle exec rubocop --only Gitlab/DelegatePredicateMethods --parallel

# Before
26639 files inspected, 10 offenses detected

# After
26639 files inspected, 9 offenses detected

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.