feat(tpl): remove dir class name from parent-dir item

Remove `dir` class name from parent-dir item.
Keep the `parent` class name.

Author: marjune163

src/tpl/frontend/index.html

@@ -84,7 +84,7 @@
 		<a class="field time" href="{{.SubItemPrefix}}{{.Context.QueryStringOfSort .SortState.NextTimeSort}}">{{.Trans.ListTimeLabel}}{{if eq $sortKey "t"}}&uarr;{{else if eq $sortKey "T"}}&darr;{{end}}</a>
 		</span>
 	</li>
-	<li class="dir parent">
+	<li class="parent">
 		<a href="{{if .IsRoot}}./{{else}}../{{end}}{{$contextQueryString}}" class="detail">
 			<span class="field name">../</span>
 			<span class="field size"></span>