Updating Converse upstream (with bootstrap5):

* bootstrap 5 compatibility
* other Converse updates integration
* hack to get the sidebar work as with Converse v10.
* modal onHide was renamed close.
* fix slow mode infobox margin.
* fix margin
* shorter action label, for better dropdown UX.

conversejs/custom/plugins/poll/templates/poll-form.js

@@ -44,7 +44,7 @@ export function tplPollForm (el) {
 
             ${formFieldTemplates}
 
-            <fieldset class="buttons form-group">
+            <fieldset class="buttons">
               <input type="submit" class="btn btn-primary" value="${i18nOk}" />
             </fieldset>
           </form>`