Build fixed for http://trac.webkit.org/changeset/128243

Unreviewed build fix.

Removed temporarily added function signature.

* icu/unicode/unistr.h:
(UnicodeString::extract):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@128340 268f45cc-cd09-0410-ab3c-d52691b4dbfc