Ensure that leave_url pages have Rails initialized

On these pages we need Rails initialized immediately in order to be able
to get the confirmation dialog toggled. As we defer initialization in
main.js, it might be too late.

app/assets/javascripts/namespaces/leave_by_url.js

+import { initRails } from '~/lib/utils/rails_ujs';
 import { deprecatedCreateFlash as Flash } from '~/flash';
 import { __, sprintf } from '~/locale';
 import { getParameterByName } from '~/lib/utils/common_utils';
@@ -11,6 +12,8 @@ export default function leaveByUrl(namespaceType) {
   const param = getParameterByName(PARAMETER_NAME);
   if (!param) return;
 
+  initRails();
+
   const leaveLink = document.querySelector(LEAVE_LINK_SELECTOR);
   if (leaveLink) {
     leaveLink.click();