Remove deprecated call in BuildSuccessWorker

We now create_deployment on Ci::Build create.
No need to call create_deployment again

app/workers/build_success_worker.rb

@@ -9,7 +9,6 @@ class BuildSuccessWorker
   # rubocop: disable CodeReuse/ActiveRecord
   def perform(build_id)
     Ci::Build.find_by(id: build_id).try do |build|
-      create_deployment(build) if build.has_environment?
       stop_environment(build) if build.stops_environment?
     end
   end
@@ -17,17 +16,6 @@ class BuildSuccessWorker
 
   private
 
-  ##
-  # Deprecated:
-  # As of 11.5, we started creating a deployment record when ci_builds record is created.
-  # Therefore we no longer need to create a deployment, after a build succeeded.
-  # We're leaving this code for the transition period, but we can remove this code in 11.6.
-  def create_deployment(build)
-    build.create_deployment.try do |deployment|
-      deployment.succeed
-    end
-  end
-
   ##
   # TODO: This should be processed in DeploymentSuccessWorker once we started storing `action` value in `deployments` records
   def stop_environment(build)

spec/workers/build_success_worker_spec.rb

@@ -6,51 +6,7 @@ describe BuildSuccessWorker do
   describe '#perform' do
     subject { described_class.new.perform(build.id) }
 
-    before do
-      allow_any_instance_of(Deployment).to receive(:create_ref)
-    end
-
     context 'when build exists' do
-      context 'when deployment was not created with the build creation' do # An edge case during the transition period
-        let!(:build) { create(:ci_build, :deploy_to_production) }
-
-        before do
-          allow(Deployments::FinishedWorker).to receive(:perform_async)
-          Deployment.delete_all
-          build.reload
-        end
-
-        it 'creates a successful deployment' do
-          expect(build).not_to be_has_deployment
-
-          subject
-
-          build.reload
-          expect(build).to be_has_deployment
-          expect(build.deployment).to be_success
-        end
-      end
-
-      context 'when deployment was created with the build creation' do # Counter part of the above edge case
-        let!(:build) { create(:ci_build, :deploy_to_production) }
-
-        it 'does not create a new deployment' do
-          expect(build).to be_has_deployment
-
-          expect { subject }.not_to change { Deployment.count }
-        end
-      end
-
-      context 'when build is not associated with project' do
-        let!(:build) { create(:ci_build, project: nil) }
-
-        it 'does not create deployment' do
-          subject
-
-          expect(build.reload).not_to be_has_deployment
-        end
-      end
-
       context 'when the build will stop an environment' do
         let!(:build) { create(:ci_build, :stop_review_app, environment: environment.name, project: environment.project) }
         let(:environment) { create(:environment, state: :available) }