Pass formats explicitly when rendering .md file

Changelog: other
EE: true

ee/app/services/issues/build_from_vulnerability_service.rb

@@ -18,7 +18,8 @@ module Issues
 
     def render_description(vulnerability)
       ApplicationController.render(
-        template: 'vulnerabilities/issue_description.md.erb',
+        template: 'vulnerabilities/issue_description',
+        formats: :md,
         locals: { vulnerability: vulnerability.present }
       )
     end