Fix typo in README (roboll#2006)

Author: coding4food

README.md

@@ -1182,7 +1182,7 @@ Hooks expose additional template expressions:
 
 `.Event.Name` is the name of the hook event.
 
-`.Event.Error` is the error generated by a failed release, exposed for `posysync` hooks only when a release fails, otherwise its value is `nil`.
+`.Event.Error` is the error generated by a failed release, exposed for `postsync` hooks only when a release fails, otherwise its value is `nil`.
 
 You can use the hooks event expressions to send notifications to platforms such as `Slack`, `MS Teams`, etc.