docs(acr): update AcrImageSigner role

Author: lizMSFT

articles/role-based-access-control/built-in-roles.md

@@ -191,7 +191,7 @@ The following table provides a brief description of each built-in role. Click th
 > | Built-in role | Description | ID |
 > | --- | --- | --- |
 > | <a name='acrdelete'></a>[AcrDelete](./built-in-roles/containers.md#acrdelete) | Delete repositories, tags, or manifests from a container registry. | c2f4ef07-c644-48eb-af81-4b1b4947fb11 |
-> | <a name='acrimagesigner'></a>[AcrImageSigner](./built-in-roles/containers.md#acrimagesigner) | Push trusted images to or pull trusted images from a container registry enabled for content trust. | 6cef56e8-d556-48e5-a04f-b8e64114680f |
+> | <a name='acrimagesigner'></a>[AcrImageSigner](./built-in-roles/containers.md#acrimagesigner) | Planned DEPRECATION on March 31, 2028. Grant the signing permission for content trust. As content trust is being deprecated and will be completely removed on March 31, 2028, this role will also be removed. Refer to https://aka.ms/acr/dctdeprecation for details and transition guidance. | 6cef56e8-d556-48e5-a04f-b8e64114680f |
 > | <a name='acrpull'></a>[AcrPull](./built-in-roles/containers.md#acrpull) | Pull artifacts from a container registry. | 7f951dda-4ed3-4680-a7ca-43fe172d538d |
 > | <a name='acrpush'></a>[AcrPush](./built-in-roles/containers.md#acrpush) | Push artifacts to or pull artifacts from a container registry. | 8311e382-0749-4cb8-b61a-304f252e45ec |
 > | <a name='acrquarantinereader'></a>[AcrQuarantineReader](./built-in-roles/containers.md#acrquarantinereader) | Pull quarantined images from a container registry. | cdda3590-29a3-44f6-95f2-9f980659eb04 |