Merge branch 'tasklist-fix' into 'master'

Fixed issue with tasklist toggling sidebar refresh

Closes #15270

See merge request !3782

app/views/projects/issues/update.js.haml

-$('aside.right-sidebar')[0].outerHTML = "#{escape_javascript(render 'shared/issuable/sidebar', issuable: @issue)}";
-$('aside.right-sidebar').effect('highlight');
-new IssuableContext();

app/views/projects/merge_requests/update.js.haml

-$('aside.right-sidebar')[0].outerHTML = "#{escape_javascript(render 'shared/issuable/sidebar', issuable: @merge_request)}";
-$('aside.right-sidebar').effect('highlight');
-new IssuableContext();