ls: removed isValidRemoteUtf8Url()

The function didn't do anything useful, it was just several lines
obfuscating that it was only forwarding isRemoteUrl()'s return value.

src/playlist.c

@@ -537,7 +537,7 @@ song_by_url(const char *url)
 	if (song != NULL)
 		return song;
 
-	if (isValidRemoteUtf8Url(url))
+	if (isRemoteUrl(url))
 		return song_remote_new(url);
 
 	return NULL;