Fix a bug preventing from doing subsequent edits in any Issuable sidebar

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 Issue();
+new IssuableContext();
\ No newline at end of file

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