Update README.md (#76)

Update `checkstyle based XML-Reports` url.
Because, current url is not available on master HEAD.

Author: sasezaki

README.md

@@ -3,7 +3,7 @@
 [![Continuous Integration](https://github.com/staabm/annotate-pull-request-from-checkstyle/workflows/Continuous%20Integration/badge.svg)](https://github.com/staabm/annotate-pull-request-from-checkstyle/actions)
 [![Continuous Deployment](https://github.com/staabm/annotate-pull-request-from-checkstyle/workflows/Continuous%20Deployment/badge.svg)](https://github.com/staabm/annotate-pull-request-from-checkstyle/actions)
 
-Turns [checkstyle based XML-Reports](https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/master/doc/checkstyle.xsd) into GitHub Pull Request [Annotations via the Checks API](https://docs.github.com/en/free-pro-team@latest/rest/reference/checks).
+Turns [checkstyle based XML-Reports](https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/v3.0.2/doc/schemas/fix/checkstyle.xsd) into GitHub Pull Request [Annotations via the Checks API](https://docs.github.com/en/free-pro-team@latest/rest/reference/checks).
 This script is meant for use within your GitHub Action.
 
 That means you no longer search thru your GitHub Action logfiles.