Add auditor access for group wiki

Allows the auditor user to access the wiki page within a group.

Changelog: fixed
EE: true

ee/app/policies/ee/group_policy.rb

@@ -187,6 +187,7 @@ module GroupPolicy
         enable :read_group_cycle_analytics
         enable :read_cluster
         enable :read_dependency_proxy
+        enable :read_wiki
       end
 
       rule { owner | admin }.policy do

ee/spec/policies/group_policy_spec.rb

@@ -2152,4 +2152,18 @@ def expect_private_group_permissions_as_if_non_member
       end
     end
   end
+
+  describe 'read wiki' do
+    context 'feature enabled' do
+      before do
+        stub_config(read_wiki: { enabled: true })
+      end
+
+      context 'auditor' do
+        let(:current_user) { auditor }
+
+        it { is_expected.to be_allowed(:read_wiki) }
+      end
+    end
+  end
 end