Remove the git_push_execute_all_project_hooks feature flag

This *reverse* feature flag has been operating in production for at
least 6 months. It should be safe to remove.

Since there's no behaviour change with the removal of this flag, there
is no need for a changelog entry.

app/services/git/process_ref_changes_service.rb

@@ -35,7 +35,7 @@ module Git
     end
 
     def execute_project_hooks?(changes)
-      (changes.size <= Gitlab::CurrentSettings.push_event_hooks_limit) || Feature.enabled?(:git_push_execute_all_project_hooks, project)
+      changes.size <= Gitlab::CurrentSettings.push_event_hooks_limit
     end
 
     def process_changes(ref_type, action, changes, execute_project_hooks:)

spec/services/git/process_ref_changes_service_spec.rb

@@ -55,36 +55,14 @@ describe Git::ProcessRefChangesService do
         stub_application_setting(push_event_hooks_limit: push_event_hooks_limit)
       end
 
-      context 'git_push_execute_all_project_hooks is disabled' do
-        before do
-          stub_feature_flags(git_push_execute_all_project_hooks: false)
-        end
-
-        it "calls #{push_service_class} with execute_project_hooks set to false" do
-          expect(push_service_class)
-            .to receive(:new)
-            .with(project, project.owner, hash_including(execute_project_hooks: false))
-            .exactly(changes.count).times
-            .and_return(service)
-
-          subject.execute
-        end
-      end
-
-      context 'git_push_execute_all_project_hooks is enabled' do
-        before do
-          stub_feature_flags(git_push_execute_all_project_hooks: true)
-        end
-
-        it "calls #{push_service_class} with execute_project_hooks set to true" do
-          expect(push_service_class)
-            .to receive(:new)
-            .with(project, project.owner, hash_including(execute_project_hooks: true))
-            .exactly(changes.count).times
-            .and_return(service)
+      it "calls #{push_service_class} with execute_project_hooks set to false" do
+        expect(push_service_class)
+          .to receive(:new)
+          .with(project, project.owner, hash_including(execute_project_hooks: false))
+          .exactly(changes.count).times
+          .and_return(service)
 
-          subject.execute
-        end
+        subject.execute
       end
     end