Remove the old headersclean unit test

We have configure -headersclean now

Change-Id: Iaa084ece95cefd5264a34726d85d13ea7a65016d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

tests/auto/headersclean/headersclean.pro

-QT = xmlpatterns
-load(qt_headersclean)
-DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0

tests/auto/host.pro

 TEMPLATE=subdirs
 SUBDIRS=\
-           headersclean \
+