feat: add mcp_slack_activity_list_tool_called audit action

Detected as a new audit action by the E2E runner (Unknown action detected).
Adds the constant alongside the other mcp_slack_*_tool_called entries.

❤️
Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

Author: zimeg

slack-api-client/src/main/java/com/slack/api/audit/Actions.java

@@ -312,6 +312,7 @@ private WorkspaceOrOrg() {
         public static final String mcp_slack_get_workflow_execution_status_tool_called = "mcp_slack_get_workflow_execution_status_tool_called";
         public static final String mcp_slack_canvas_find_replace_tool_called = "mcp_slack_canvas_find_replace_tool_called";
         public static final String mcp_slack_list_workflows_tool_called = "mcp_slack_list_workflows_tool_called";
+        public static final String mcp_slack_activity_list_tool_called = "mcp_slack_activity_list_tool_called";
         public static final String mcp_slack_run_workflow_tool_called = "mcp_slack_run_workflow_tool_called";
         public static final String slack_ai_mcp_tool_called = "slack_ai_mcp_tool_called";
         public static final String slack_ai_mcp_tool_permission_changed = "slack_ai_mcp_tool_permission_changed";