Fix user privileges (#1966) (#1968)

* Revert "IndicesPrivileges can contain multiple queries (#1963)"

This reverts commit 3bc6627.

* Fix IndicesPrivileges and RoleTemplateScript

Co-authored-by: Sylvain Wallez <sylvain@elastic.co>

Author: github-actions[bot]

output/schema/schema.json

@@ -21,5 +21,5 @@ import { Fields } from '@_types/common'
 
 export class FieldSecurity {
   except?: Fields
-  grant: Fields
+  grant?: Fields
 }