[New Multicolumn]Remove assert in RenderMultiColumnFlowThread::createAnonymous
https://bugs.webkit.org/show_bug.cgi?id=113855

Reviewed by Antti Koivisto.

Remove CSSRegions specific assert from new multicolumn implementation.
No change in functionality, no new tests.

* rendering/RenderMultiColumnFlowThread.cpp:
(WebCore::RenderMultiColumnFlowThread::createAnonymous):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147531 268f45cc-cd09-0410-ab3c-d52691b4dbfc