Update index.md

Author: joeynmq

src/connections/destinations/catalog/klaviyo/index.md

@@ -85,6 +85,8 @@ If your `userId` is an email, or you provide an email in `traits.email`, Segment
 #### Enforce email as primary identifier
 
 This option is enabled by default to ensure duplicate profiles are not being created inside of Klaviyo. When enabled, Segment will never set the $id field to your `userId` when you call `.identify()` or `.track()`. Instead, Segment will only set $email as the primary identifier with your `traits.email` or `properties.email`. Please note that if you have this setting toggled on, you must send `email` in on your payloads or your events will not go through to Klaviyo.
+> info ""
+> For the Web Device-mode connection, this option applies **only** to the `.identify()` call.
 
 #### Fallback on Anonymous ID