It's now updated so we could remove it

Updated in:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17673

lib/tasks/haml-lint.rake

@@ -2,14 +2,5 @@ unless Rails.env.production?
   require 'haml_lint/rake_task'
   require 'haml_lint/inline_javascript'
 
-  # Workaround for warnings from parser/current
-  # TODO: Remove this after we update parser gem
-  task :haml_lint do
-    require 'parser'
-    def Parser.warn(*args)
-      puts(*args) # static-analysis ignores stdout if status is 0
-    end
-  end
-
   HamlLint::RakeTask.new
 end