Add changelog item

Author: phylor

CHANGELOG.md

@@ -4,6 +4,8 @@ Note: For changes to the API, see https://shopify.dev/changelog?filter=api
 
 ## Unreleased
 
+- Fix webhook requests when a header is present having a symbol key (e.g. `:clearance`)
+
 ## Version 10.1.0
 
 - [#933](https://github.com/Shopify/shopify_api/pull/933) Fix syntax of GraphQL query in `Webhooks.get_webhook_id` method by removing extra curly brace