style(test): improve Ruby style

test/integration/repo/controls/packages_spec.rb

@@ -1,23 +1,24 @@
 # frozen_string_literal: true
 
+control 'prometheus packages' do
+  title 'should be installed'
+
+  packages =
     case platform[:family]
     when 'redhat'
-  packages = %w[
+      %w[
         prometheus2
         alertmanager
         node_exporter
       ]
     when 'debian'
-  packages = %w[
+      %w[
         prometheus
         prometheus-alertmanager
         prometheus-node-exporter
       ]
     end
 
-control 'prometheus packages' do
-  title 'should be installed'
-
   packages.each do |p|
     describe package(p) do
       it { should be_installed }