add `x-ms-enum` for alertsmanagement#17225

lirenhe merged 2 commits intoAzure:mainAzure/azure-rest-api-specs:mainfrom

ArcturusZhang:x-ms-enum-alertsmanagementArcturusZhang/azure-rest-api-specs:x-ms-enum-alertsmanagementCopy head branch name to clipboard