tools: support a toc for projects, with single exposing module, in v doc (#19001)

Author: ttytm

cmd/tools/vdoc/html.v

@@ -261,7 +261,7 @@ fn (vd VDoc) gen_html(d doc.Doc) string {
 	} else {
 		symbols_toc_str
 	}).replace('{{ contents }}', contents.str()).replace('{{ right_content }}', if cfg.is_multi
-		&& vd.docs.len > 1 && d.head.name != 'README' {
+		&& d.head.name != 'README' {
 		'<div class="doc-toc"><ul>' + symbols_toc_str + '</ul></div>'
 	} else {
 		''