Fix typo in CHANGELOG.md (#59)

Author: fnesveda

CHANGELOG.md

@@ -7,7 +7,7 @@ Changelog
 ### Changed
 
 - replaced `base_url` with `api_url` in the client constructor
-  to enable easier passing of the API server url from environment variables availabl to actors on the Apify platform
+  to enable easier passing of the API server url from environment variables available to actors on the Apify platform
 - added the `gracefully` parameter to the "Abort run" method
 
 ### Internal changes