Add rule about kubectl to example guidelines doc.

examples/guidelines.md

@@ -110,7 +110,8 @@ Examples are not:
 * When providing an example command or config for which the user is
   expected to substitute text with something specific to them, use
   angle brackets: `<IDENTIFIER>` for the text to be substituted.
-
+* Use `kubectl` instead of `cluster\kubectl.sh` for example cli
+  commands.
 
 ### At the end