Fix rubocop array literal in loop in spec/db/docs_spec.rb

What does this MR do and why?

Fix rubocop array literal in loop in spec/db/docs_spec.rb

This is causing a master broken in gitlab-org/quality/engineering-productivity/master-broken-incidents#4019 (closed)

See the failed job https://gitlab.com/gitlab-org/gitlab/-/jobs/5433189088 :

Offenses:
spec/db/docs_spec.rb:173:80: C: Performance/CollectionLiteralInLoop: Avoid immutable Array literals in loops. It is better to extract it into a local variable or a constant.
  database_base_models = Gitlab::Database.database_base_models.select { |k, _| %w[geo jh].exclude?(k) }
                                                                               ^^^^^^^^^^
spec/db/docs_spec.rb:182:80: C: Performance/CollectionLiteralInLoop: Avoid immutable Array literals in loops. It is better to extract it into a local variable or a constant.
  database_base_models = Gitlab::Database.database_base_models.select { |k, _| %w[geo jh].exclude?(k) }
                                                                               ^^^^^^^^^^
34087 files inspected, 2 offenses detected

This was merged in !133566 (merged) and must have somehow conflicted with a rubocop rule we were adding.

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