Add deprecation warning for old CI status badge action

We keep this only for backwards compatibility with projects that have
been migrated from GitLab CI. New project badge will go elsewhere.

app/controllers/ci/projects_controller.rb

@@ -12,9 +12,12 @@ module Ci
 
     # Project status badge
     # Image with build status for sha or ref
+    #
+    # This action in DEPRECATED, this is here only for backwards compatibility
+    # with projects migrated from GitLab CI.
+    #
     def badge
       image = Ci::ImageForBuildService.new.execute(@project, params)
-
       send_file image.path, filename: image.name, disposition: 'inline', type:"image/svg+xml"
     end