correctly init GFM

app/assets/javascripts/pages/groups/milestones/edit/index.js

 import initForm from '../../../../shared/milestones/form';
 
-export default () => initForm();
+export default () => initForm(false);

app/assets/javascripts/pages/groups/milestones/new/index.js

 import initForm from '../../../../shared/milestones/form';
 
-export default () => initForm();
+export default () => initForm(false);

app/assets/javascripts/shared/milestones/form.js

@@ -2,8 +2,8 @@ import ZenMode from '../../zen_mode';
 import DueDateSelectors from '../../due_date_select';
 import GLForm from '../../gl_form';
 
-export default () => {
+export default (initGFM = true) => {
   new ZenMode(); // eslint-disable-line no-new
   new DueDateSelectors(); // eslint-disable-line no-new
-  new GLForm($('.milestone-form'), true); // eslint-disable-line no-new
+  new GLForm($('.milestone-form'), initGFM); // eslint-disable-line no-new
 };