Add CSV import activity types to admin activity logs (#377)

* feat: Add csv_import_creation and csv_import_completion activity types

Add two new activity log event types for CSV import tracking to the
OpenAPI spec enum (v2.14 and v2.15).

Tracking issue: intercom/intercom#473387

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: Remove csv_import event types from 2.14 version

Only keep in 2.15 (latest) since this repo has no Unstable version.
Per API versioning policy, avoid shipping to previous versions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: thibault-intercom

descriptions/2.15/api.intercom.io.yaml

@@ -14743,6 +14743,8 @@ components:
           - conversation_topic_change
           - conversation_topic_creation
           - conversation_topic_deletion
+          - csv_import_completion
+          - csv_import_creation
           - custom_authentication_token_creation
           - help_center_settings_change
           - inbound_conversations_change