Add GitHub Sync activity log event types to the enum

Registers github_sync_disconnected and github_sync_cleanup_deleted_folder
in the 2.15 activity-log event-type enum.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: bhavishnadar

descriptions/2.15/api.intercom.io.yaml

@@ -15049,6 +15049,8 @@ components:
           - csv_import_completion
           - csv_import_creation
           - custom_authentication_token_creation
+          - github_sync_cleanup_deleted_folder
+          - github_sync_disconnected
           - help_center_settings_change
           - inbound_conversations_change
           - inbox_access_change