update the webhook execution to return milliseconds

Author: matthewlouisbrockman

docs/sandbox/lifecycle-events-webhooks.mdx

@@ -262,7 +262,7 @@ The payload structure matches the event format from the API:
       "started_at": "2025-08-06T20:58:24Z",
       "vcpu_count": 2,
       "memory_mb": 512,
-      "execution_time": 1.0,
+      "execution_time": 1000,
     }
   },
   "sandboxBuildId": "<template-build-id>",
@@ -279,7 +279,7 @@ The payload structure matches the event format from the API:
 - `started_at` - UTC RFC3339 timestamp when the current sandbox execution started
 - `vcpu_count` - Number of vCPUs assigned to the sandbox
 - `memory_mb` - Memory assigned to the sandbox in MB
-- `execution_time` - Sandbox runtime in seconds
+- `execution_time` - Sandbox runtime in milliseconds
 
 # Webhook verification
 To ensure the authenticity of webhook requests, each request includes a signature in the `e2b-signature` header.