Remove this old check for Opera

This Opera workaround originally came from jqueryUI's datepicker. It's since been removed:
https://github.com/jquery/jquery-ui/commit/30c064427bc697bce992c68ce2db7ddd529c76e9

I've created a fiddle that shows the timepicker within a fixed element which still works in Opera 12 regardless of the override being in place: http://jsfiddle.net/mzkc4/5/
My guess is the Opera devs wrote in a workaround for the workaround...

Timepicker should remove this check, too. With jQuery 1.9, having the $.browser call causes a runtime error.