Fix visibility of the title of Google maps popups

ref https://www.woltlab.com/community/thread/316666-karte-farben-von-hintergrund-und-text-in-popups/

Author: BurntimeX

wcfsetup/install/files/style/ui/googleMap.scss

@@ -73,3 +73,7 @@
 		color: #369;
 	}
 }
+
+.gm-style-iw-ch {
+	color: #333;
+}