fix: correct AlertPolicy import formats (#15777)

Author: nika-pr

mmv1/products/monitoring/AlertPolicy.yaml

@@ -29,8 +29,7 @@ update_verb: 'PATCH'
 update_mask: true
 mutex: 'alertPolicy/{{project}}'
 import_format:
-  - '{{project}} {{name}}'
-  - '{{name}}'
+  - 'projects/{{project}}/alertPolicies/{{name}}'
 timeouts:
   insert_minutes: 20
   update_minutes: 20