Remove the check_maven_path_first feature flag

Update the related specs

Changelog: other

config/feature_flags/development/check_maven_path_first.yml

----
-name: check_maven_path_first
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/59241
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/327487
-milestone: '13.11'
-type: development
-group: group::package
-default_enabled: true

lib/api/maven_packages.rb

@@ -24,8 +24,6 @@ module API
 
     helpers do
       def path_exists?(path)
-        # return true when FF disabled so that processing the request is not stopped
-        return true unless Feature.enabled?(:check_maven_path_first, default_enabled: :yaml)
         return false if path.blank?
 
         Packages::Maven::Metadatum.with_path(path)