Align unit tests with code

The code is only executed on osfamily RedHat with major version below 7.
The unit tests did only skip the tests on RedHat 7 but not on 8.

Removes errors:
rspec './spec/classes/update_spec.rb[1:9:3:1]' # ca_cert::update on redhat-8-x86_64 with force_enable set to true is expected to contain Exec[enable_ca_trust] with command => "update-ca-trust force-enable"
rspec './spec/classes/update_spec.rb[1:9:4:1]' # ca_cert::update on redhat-8-x86_64 with force_enable set to false is expected to contain Exec[enable_ca_trust] with command => "update-ca-trust enable"

spec/classes/update_spec.rb

@@ -21,7 +21,7 @@
           )
         }
       when 'RedHat'
-        if facts[:os]['release']['major'] == '7'
+        if facts[:os]['release']['major'] >= '7'
           it { is_expected.not_to contain_exec('enable_ca_trust') }
         else
           context 'with force_enable set to true' do