feat(firebase): update the API

#### firebase:v1beta1

The following keys were added:
- schemas.MessageSet.deprecated
- schemas.MessageSet.description

Author: yoshi-automation

discovery/firebase-v1beta1.json

@@ -1324,7 +1324,7 @@
       }
     }
   },
-  "revision": "20250314",
+  "revision": "20250331",
   "rootUrl": "https://firebase.googleapis.com/",
   "schemas": {
     "AddFirebaseRequest": {
@@ -1919,6 +1919,8 @@
       "type": "object"
     },
     "MessageSet": {
+      "deprecated": true,
+      "description": "This is proto2's version of MessageSet. DEPRECATED: DO NOT USE FOR NEW FIELDS. If you are using editions or proto2, please make your own extendable messages for your use case. If you are using proto3, please use `Any` instead. MessageSet was the implementation of extensions for proto1. When proto2 was introduced, extensions were implemented as a first-class feature. This schema for MessageSet was meant to be a \"bridge\" solution to migrate MessageSet-bearing messages from proto1 to proto2. This schema has been open-sourced only to facilitate the migration of Google products with MessageSet-bearing messages to open-source environments.",
       "id": "MessageSet",
       "properties": {},
       "type": "object"

src/apis/firebase/v1beta1.ts

@@ -504,6 +504,9 @@ export namespace firebase_v1beta1 {
      */
     type?: string | null;
   }
+  /**
+   * This is proto2's version of MessageSet. DEPRECATED: DO NOT USE FOR NEW FIELDS. If you are using editions or proto2, please make your own extendable messages for your use case. If you are using proto3, please use `Any` instead. MessageSet was the implementation of extensions for proto1. When proto2 was introduced, extensions were implemented as a first-class feature. This schema for MessageSet was meant to be a "bridge" solution to migrate MessageSet-bearing messages from proto1 to proto2. This schema has been open-sourced only to facilitate the migration of Google products with MessageSet-bearing messages to open-source environments.
+   */
   export interface Schema$MessageSet {}
   /**
    * This resource represents a long-running operation that is the result of a network API call.