Refs #36998 - disable Rails/ContentTag cop

The cop is buggy before rubocop-rails 2.12.0 [1][2], but to get that
we'd need a newer theforeman-rubocop, which generates more offenses than
I am willing to fix today. Disable the cop like it was disabled in
foreman_ansible too [3].

[1] rubocop/rubocop-rails#260
[2] rubocop/rubocop-rails#526
[3] theforeman/foreman_ansible#357

(cherry picked from commit 98c9fee)

.rubocop.yml

@@ -11,6 +11,9 @@ inherit_from:
 Rails:
   Enabled: true
 
+Rails/ContentTag:
+  Enabled: false
+
 AllCops:
   Exclude:
     - db/migrate/20131014135042_katello_tables.rb