Simplify condition for group dashboard

ee/app/policies/ee/group_policy.rb

@@ -25,8 +25,8 @@ module EE
         ::Gitlab::CurrentSettings.lock_memberships_to_ldap?
       end
 
-      condition(:security_dashboard_feature_disabled) do
-        !@subject.feature_available?(:security_dashboard)
+      condition(:security_dashboard_feature_enabled) do
+        @subject.feature_available?(:security_dashboard)
       end
 
       condition(:needs_new_sso_session) do
@@ -129,13 +129,10 @@ module EE
       end
 
       rule { developer }.policy do
-        enable :read_group_security_dashboard
         enable :admin_merge_request
       end
 
-      rule { security_dashboard_feature_disabled }.policy do
-        prevent :read_group_security_dashboard
-      end
+      rule { security_dashboard_feature_enabled & developer }.enable :read_group_security_dashboard
 
       rule { needs_new_sso_session }.policy do
         prevent :read_group