Update inventory script visibility access level

admin roles on inv scripts can now see the actual script contents.  Read
role doesn't convey that capability.

This should be pretty similar to before from a read_role
perspective... it now allows more folks to see the script contents

awx/api/serializers.py

@@ -1279,7 +1279,7 @@ class CustomInventoryScriptSerializer(BaseSerializer):
         if obj is None:
             return ret
         request = self.context.get('request', None)
-        if request is not None and request.user is not None and not request.user.is_superuser:
+        if not request.user in obj.admin_role:
             ret['script'] = None
         return ret