Update reference URL in "Check License" workflow

GitHub has changed the URL of this documentation page. Even though the old one redirects to the new one, it's best not to
rely on that. And anyway, the new URL is nicer.

Author: per1234

.github/workflows/check-license.yml

@@ -5,7 +5,7 @@ env:
   # SPDX identifier: https://spdx.org/licenses/
   EXPECTED_LICENSE_TYPE: CC0-1.0
 
-# See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
+# See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
     paths: