Revert "CentOS 9: Disable unit tests dependent on puppet-postgresql"

This reverts commit b8c3e8cb71.

Reason for revert:
puppet-postgresql 8.1.0 was released and now the module supports RHEL 9
(and CentOS 9 effectively).

Note:
This change adds the service_provider fact in test fact data because
it is required by puppet-postgresql.

Depends-on: https://review.opendev.org/850705
Change-Id: I811c35baba816e1340d857f2e5113487500c315f

spec/classes/heat_db_postgresql_spec.rb

@@ -35,15 +35,13 @@ describe 'heat::db::postgresql' do
     context "on #{os}" do
       let (:facts) do
         facts.merge(OSDefaults.get_facts({
-          :os_workers => 8,
-          :concat_basedir => '/var/lib/puppet/concat'
+          # puppet-postgresql requires the service_provider fact provided by
+          # puppetlabs-postgresql.
+          :service_provider => 'systemd'
         }))
       end
 
-      # TODO(tkajinam): Remove this once puppet-postgresql supports CentOS 9
-      unless facts[:osfamily] == 'RedHat' and facts[:operatingsystemmajrelease].to_i >= 9
-        it_behaves_like 'heat::db::postgresql'
-      end
+      it_behaves_like 'heat::db::postgresql'
     end
   end