Remove FF verification_state_backfill_worker

Changelog: added
EE: true

ee/app/models/concerns/geo/verifiable_replicator.rb

@@ -51,7 +51,7 @@ module Geo
 
         ::Geo::ReverificationBatchWorker.perform_with_capacity(replicable_name)
 
-        if Feature.enabled?(:verification_state_backfill_worker, default_enabled: :yaml) && verification_query_class.separate_verification_state_table?
+        if verification_query_class.separate_verification_state_table?
           ::Geo::VerificationStateBackfillWorker.perform_async(replicable_name)
         end
       end

ee/config/feature_flags/development/verification_state_backfill_worker.yml

----
-name: verification_state_backfill_worker
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/69301
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/340648
-milestone: '14.4'
-type: development
-group: group::geo
-default_enabled: false

ee/spec/support/shared_examples/models/concerns/verifiable_replicator_shared_examples.rb

@@ -144,18 +144,12 @@ RSpec.shared_examples 'a verifiable replicator' do
         described_class.trigger_background_verification
       end
 
-      context 'when verification_state_backfill_worker feature flag is enabled' do
-        before do
-          stub_feature_flags(verification_state_backfill_worker: true)
-          expect(described_class.model).to receive(:separate_verification_state_table?).and_return(true)
-        end
-
       it 'enqueues VerificationStateBackfillWorker' do
+        expect(described_class.model).to receive(:separate_verification_state_table?).and_return(true)
         expect(::Geo::VerificationStateBackfillWorker).to receive(:perform_async).with(described_class.replicable_name)
 
         described_class.trigger_background_verification
       end
-      end
 
       context 'for a Geo secondary' do
         it 'does not enqueue ReverificationBatchWorker' do