Fix some dropdown problems on the issue sidebar (#34308)

Also fix #34300

templates/repo/issue/sidebar/reviewer_list.tmpl

@@ -6,8 +6,8 @@
 		{{if $pageMeta.Issue}}data-update-url="{{$pageMeta.RepoLink}}/issues/request_review?issue_ids={{$pageMeta.Issue.ID}}"{{end}}
 >
 	<input type="hidden" class="combo-value" name="reviewer_ids">{{/* match CreateIssueForm */}}
-	<div class="ui dropdown text-flex-grow {{if or (not $hasCandidates) (not $data.CanChooseReviewer)}}disabled{{end}}">
-		<a class="text muted">
+	<div class="ui dropdown full-width {{if or (not $hasCandidates) (not $data.CanChooseReviewer)}}disabled{{end}}">
+		<a class="fixed-text muted">
 			<strong>{{ctx.Locale.Tr "repo.issues.review.reviewers"}}</strong> {{if $data.CanChooseReviewer}}{{svg "octicon-gear"}}{{end}}
 		</a>
 		<div class="menu flex-items-menu">