Remove optimize_safe_find_or_create_by FF

Removes the feature flag for optimizing safe_find_or_create_by to reduce
subtransactions

Changelog: other

app/models/application_record.rb

@@ -64,14 +64,6 @@ class ApplicationRecord < ActiveRecord::Base
   end
 
   def self.safe_find_or_create_by(*args, &block)
-    return optimized_safe_find_or_create_by(*args, &block) if Feature.enabled?(:optimize_safe_find_or_create_by, default_enabled: :yaml)
-
-    safe_ensure_unique(retries: 1) do # rubocop:disable Performance/ActiveRecordSubtransactionMethods
-      find_or_create_by(*args, &block)
-    end
-  end
-
-  def self.optimized_safe_find_or_create_by(*args, &block)
     record = find_by(*args)
     return record if record.present?
 

config/feature_flags/development/optimize_safe_find_or_create_by.yml

----
-name: optimize_safe_find_or_create_by
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68458
-rollout_issue_url: 
-milestone: '14.3'
-type: development
-group: group::database
-default_enabled: false

spec/models/application_record_spec.rb

@@ -39,7 +39,7 @@ RSpec.describe ApplicationRecord do
 
     let(:suggestion_attributes) { attributes_for(:suggestion).merge!(note_id: note.id) }
 
-    shared_examples '.safe_find_or_create_by' do
+    describe '.safe_find_or_create_by' do
       it 'creates the suggestion avoiding race conditions' do
         existing_suggestion = double(:Suggestion)
 
@@ -63,7 +63,7 @@ RSpec.describe ApplicationRecord do
       end
     end
 
-    shared_examples '.safe_find_or_create_by!' do
+    describe '.safe_find_or_create_by!' do
       it 'creates a record using safe_find_or_create_by' do
         expect(Suggestion.safe_find_or_create_by!(suggestion_attributes))
           .to be_a(Suggestion)
@@ -88,24 +88,6 @@ RSpec.describe ApplicationRecord do
           .to raise_error(ActiveRecord::RecordNotFound)
       end
     end
-
-    context 'when optimized_safe_find_or_create_by is enabled' do
-      before do
-        stub_feature_flags(optimized_safe_find_or_create_by: true)
-      end
-
-      it_behaves_like '.safe_find_or_create_by'
-      it_behaves_like '.safe_find_or_create_by!'
-    end
-
-    context 'when optimized_safe_find_or_create_by is disabled' do
-      before do
-        stub_feature_flags(optimized_safe_find_or_create_by: false)
-      end
-
-      it_behaves_like '.safe_find_or_create_by'
-      it_behaves_like '.safe_find_or_create_by!'
-    end
   end
 
   describe '.underscore' do