Remove ci_drop_new_builds_when_ci_quota_exceeded feature flag

Fail created jobs when CI minutes quota exceeded

Changelog: added
EE: true

config/feature_flags/development/ci_drop_new_builds_when_ci_quota_exceeded.yml

----
-name: ci_drop_new_builds_when_ci_quota_exceeded
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61166
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/326709
-milestone: '14.0'
-type: development
-group: group::pipeline execution
-default_enabled: false

ee/app/services/ci/pipeline_creation/drop_not_runnable_builds_service.rb

@@ -13,7 +13,6 @@ module Ci
       # before the first pipeline processing call
       #
       def execute
-        return unless ::Feature.enabled?(:ci_drop_new_builds_when_ci_quota_exceeded, project, default_enabled: :yaml)
         return unless pipeline.created?
 
         validate_build_matchers

ee/spec/services/ci/pipeline_creation/drop_not_runnable_builds_service_spec.rb

@@ -77,14 +77,6 @@ RSpec.describe Ci::PipelineCreation::DropNotRunnableBuildsService do
         it_behaves_like 'jobs allowed to run'
       end
 
-      context 'when the feature flag is disabled' do
-        before do
-          stub_feature_flags(ci_drop_new_builds_when_ci_quota_exceeded: false)
-        end
-
-        it_behaves_like 'jobs allowed to run'
-      end
-
       context 'when the pipeline status is running' do
         before do
           pipeline.update!(status: :running)