Revert "prevent issues with css selectors conainting braces. See https://code.google.com/p/cssjanus/issues/detail?id=22. Already fixed in MediaWiki php port."

This reverts commit 7918665d95158ece114aaf2451b893501d94a13e.
Prevent issues with css selectors containing parentheses

See https://code.google.com/p/cssjanus/issues/detail?id=22

This has already fixed in MediaWiki php port -
https://doc.wikimedia.org/mediawiki-core/master/php/html/CSSJanus_8php_s
ource.html