Remove TextIterator.cpp's isAllCollapsibleWhitespace
https://bugs.webkit.org/show_bug.cgi?id=112200

Reviewed by Ryosuke Niwa.

Remove isAllCollapsibleWhitespace since nothing uses it.

* editing/TextIterator.cpp: Remove isAllCollapsibleWhitespace.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145613 268f45cc-cd09-0410-ab3c-d52691b4dbfc