build: update generated rpm spec to drop Group: keyword
build: update generated rpm spec to drop Group: keyword

Has been deprecated for years apparently, recently removed
from Fedora in its entirety.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp