feat(walletobjects): update the API

#### walletobjects:v1

The following keys were added:
- schemas.Blobstore2Info.properties.downloadExternalReadToken.description
- schemas.Blobstore2Info.properties.downloadExternalReadToken.format
- schemas.Blobstore2Info.properties.downloadExternalReadToken.type

Author: yoshi-automation

discovery/walletobjects-v1.json

@@ -2711,7 +2711,7 @@
       }
     }
   },
-  "revision": "20250909",
+  "revision": "20251202",
   "rootUrl": "https://walletobjects.googleapis.com/",
   "schemas": {
     "ActivationOptions": {
@@ -3026,6 +3026,11 @@
           "description": "The blob id, e.g., /blobstore/prod/playground/scotty",
           "type": "string"
         },
+        "downloadExternalReadToken": {
+          "description": "A serialized External Read Token passed from Bigstore -> Scotty for a GCS download. This field must never be consumed outside of Bigstore, and is not applicable to non-GCS media uploads.",
+          "format": "byte",
+          "type": "string"
+        },
         "downloadReadHandle": {
           "description": "Read handle passed from Bigstore -> Scotty for a GCS download. This is a signed, serialized blobstore2.ReadHandle proto which must never be set outside of Bigstore, and is not applicable to non-GCS media downloads.",
           "format": "byte",