Fix incorrect pathname in comment

Change-Id: Icd5bbba4e20fb5fbd24fede1318a2dd21a673601
The URE unorc is now set up in instsetoo_native/CustomTarget_setup.mk

So no need to expand it at configure time in ure/source/unorc, and no need to
handle the related builddir!=srcdir complications.

Change-Id: Ifa34d25fab9ad2da13ed039bf6c5921b0fb58703