install-deps.sh: Make powertools repo case insensitive

install-deps.sh: Make powertools repo case insensitive

It looks like CentOS 8.3 will see all repos converted to lower case and
this has been pre-empted in the CentOS stream repos so we need to be
able to enable a repo called 'PowerTools' or 'powertools'

See https://git.centos.org/rpms/centos-repos/c/b759b17

Fixes: https://tracker.ceph.com/issues/48174
Signed-off-by: Brad Hubbard <bhubbard@redhat.com>
(cherry picked from commit 7a68845579c701f43c9526c810e586680cf76fe0)

 Conflicts:
	install-deps.sh - minor formatiing difference