update docs

CHANGES.md

@@ -4,8 +4,11 @@
 
 ### BREAKING CHANGES
 
+* GROWI no longer supports Crowi Classic Authentication
 * GROWI no longer supports [Crowi Template syntax](https://medium.com/crowi-book/crowi-v1-5-0-5a62e7c6be90)
 
+Upgrading Guide: https://docs.growi.org/guide/upgrading/35x.html
+
 ### Updates
 
 * Feature: Comment Thread