Removed '.ui-widget :active' selector because of the performance problem

I found a very slow selector:

    .ui-widget :active {
      outline: none;
    }

I have a complex HTML page containing a large grid (with more than 500 rows). After importing `jq-ui-bootstrap.less` every click lasts about 500ms. Delay is the same even if there isn't any ascendant element with `.ui-widget` class.
After some experiments I found that the reason of these lags is the selector above. When I comment it, all works fine. I don't know why this selector is so slow, but it's bad practice to use the descendant selector in any case. I suppose `outline: none` was introduced mostly for `<a>` tags. But it was already done in Bootstrap, see 'normalize.less':

    a:active,
    a:hover {
      outline: 0;
    }

So I think the selector `.ui-widget :active` can be safely deleted.