Update Admin Activity Logs API with granular assignment limit types (#293)

This change introduces granular activity types for admin assignment limit changes,
allowing developers to distinguish between conversation and ticket assignment limits.

Changes:
- Split `admin_assignment_limit_change` into two separate activity types:
  - `admin_conversation_assignment_limit_change`
  - `admin_ticket_assignment_limit_change`
- Added new metadata fields to activity_log_metadata:
  - `conversation_assignment_limit`
  - `ticket_assignment_limit`

This is a follow-up to intercom/developer-docs#597

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: marcmlc

descriptions/0/api.intercom.io.yaml

@@ -14318,7 +14318,8 @@ components:
         activity_type:
           type: string
           enum:
-          - admin_assignment_limit_change
+          - admin_conversation_assignment_limit_change
+          - admin_ticket_assignment_limit_change
           - admin_away_mode_change
           - admin_deletion
           - admin_deprovisioned
@@ -14461,6 +14462,16 @@ components:
           nullable: true
           description: The name of the Admin who initiated the activity.
           example: Joe Example
+        conversation_assignment_limit:
+          type: integer
+          nullable: true
+          description: The conversation assignment limit value for an admin.
+          example: 15
+        ticket_assignment_limit:
+          type: integer
+          nullable: true
+          description: The ticket assignment limit value for an admin.
+          example: 20
     addressable_list:
       title: Addressable List
       type: object