[properties] remove obsolete PTAG usages

In some places, property retrievals of the form
GET_PROP...(TypeTag, PTAG(...))
can still be found. The use of PTAG is not required for a very long time
already. This patch replaces such calls by
GET_PROP...(TypeTag, ...)

Reviewed by gruenich.



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@14240 2fb0f335-1f38-0410-981e-8018bf24f1b0