Remove unnecessary call from wordcloud test

The WordCloud acceptance test was calling `world.css_has_text` without actually making an assertion.  When I refactored `css_has_text` to wait for the element to be non-blank, this caused the tests to time out.

Since `world.css_has_text` wasn't being used to assert anything and since `world.css_click` now has logic to wait for the button to be visible, I'm removing the call.

@jzoldak