[ticket/13955] Fix WebFontConig to load web fonts correctly

Fix overall_header's WebFontConfig section to load fonts correctly
in all browsers.

PHPBB3-13955

phpBB/styles/prosilver/template/overall_header.html

@@ -31,7 +31,7 @@
 <script>
 	WebFontConfig = {
 		google: {
-			families: ['Open Sans:n6']
+			families: ['Open+Sans:600:cyrillic-ext,latin,greek-ext,greek,vietnamese,latin-ext,cyrillic']
 		}
 	};