Perform Replicator#verify even if not "started"

* `Geo::VerificationWorker` is already deduplicated for identical args
  since it is marked `idempotent!`
* When `verification_state` is not `verification_started`, it is not
  necessary for `VerificationWorker#perform` or `Replicator#verify` to
  exit without doing work. Furthermore, it is unexpected.

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

@@ -126,8 +126,7 @@ module Geo
     # Calculates checksum and asks the model/registry to update verification
     # state.
     def verify
-      # Deduplicate verification job
-      return unless model_record.verification_started?
+      model_record.verification_started! unless model_record.verification_started?
 
       calculation_started_at = Time.current
       checksum = model_record.calculate_checksum

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

@@ -299,11 +299,6 @@ RSpec.shared_examples 'a verifiable replicator' do
         stub_primary_node
       end
 
-      context 'when verification was started' do
-        before do
-          model_record.verification_started!
-        end
-
       context 'when the checksum succeeds' do
         it 'delegates checksum calculation and the state change to model_record' do
           expect(model_record).to receive(:calculate_checksum).and_return('abc123')
@@ -326,14 +321,5 @@ RSpec.shared_examples 'a verifiable replicator' do
         end
       end
     end
-
-      context 'when verification was not started' do
-        it 'does not call calculate_checksum!' do
-          expect(model_record).not_to receive(:calculate_checksum)
-
-          replicator.verify
-        end
-      end
-    end
   end
 end