Avoid a duplicated SQL condition in the NPM metadata endpoint

Changelog: performance

config/feature_flags/development/npm_finder_query_avoid_duplicated_conditions.yml

----
-name: npm_finder_query_avoid_duplicated_conditions
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/69572
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/340099
-milestone: '14.3'
-type: development
-group: group::package
-default_enabled: false

lib/api/helpers/packages/npm.rb

@@ -60,7 +60,7 @@ module API
               finder = ::Packages::Npm::PackageFinder.new(
                 package_name,
                 namespace: namespace,
-                last_of_each_version: Feature.disabled?(:npm_finder_query_avoid_duplicated_conditions)
+                last_of_each_version: false
               )
 
               finder.last&.project_id

spec/requests/api/npm_instance_packages_spec.rb

@@ -10,7 +10,6 @@ RSpec.describe API::NpmInstancePackages do
 
   include_context 'npm api setup'
 
-  shared_examples 'handling all endpoints' do
   describe 'GET /api/v4/packages/npm/*package_name' do
     it_behaves_like 'handling get metadata requests', scope: :instance do
       let(:url) { api("/packages/npm/#{package_name}") }
@@ -34,15 +33,4 @@ RSpec.describe API::NpmInstancePackages do
       let(:url) { api("/packages/npm/-/package/#{package_name}/dist-tags/#{tag_name}") }
     end
   end
-  end
-
-  it_behaves_like 'handling all endpoints'
-
-  context 'with npm_finder_query_avoid_duplicated_conditions disabled' do
-    before do
-      stub_feature_flags(npm_finder_query_avoid_duplicated_conditions: false)
-    end
-
-    it_behaves_like 'handling all endpoints'
-  end
 end