Fix Style/IfUnlessModifier offences

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What does this MR do and why?

Fixing offences for -

    - 'app/models/ci/running_build.rb'
    - 'app/models/clusters/cluster.rb'
    - 'app/models/clusters/clusters_hierarchy.rb'
    - 'app/models/clusters/platforms/kubernetes.rb'
    - 'app/models/commit.rb'
    - 'app/models/concerns/atomic_internal_id.rb'
    - 'app/models/concerns/avatarable.rb'
    - 'app/models/concerns/bulk_insert_safe.rb'
    - 'app/models/concerns/bulk_insertable_associations.rb'
    - 'app/models/concerns/bulk_users_by_email_load.rb'
    - 'app/models/concerns/cache_markdown_field.rb'

Related to #239356