update config docs url (#26640)

Author: techknowlogick

custom/conf/app.example.ini

@@ -4,7 +4,7 @@
 ;; Do not copy the whole file as-is, as it contains some invalid sections for illustrative purposes.
 ;; If you don't know what a setting is you should not set it.
 ;;
-;; see https://docs.gitea.io/en-us/config-cheat-sheet/ for additional documentation.
+;; see https://docs.gitea.com/administration/config-cheat-sheet for additional documentation.
 
 
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