Remove broken example from Makefile (#9159)

* Remove broken example from Makefile

* Correct example in Vagrantfile

Makefile

@@ -295,7 +295,7 @@ define PARSE_RULE
         $$(info |     make project_folder:keymap[:target])
         $$(info |  Examples:)
         $$(info |     make planck/rev4:default:dfu)
-        $$(info |     make planck:default)
+        $$(info |     make planck/rev4:default)
         $$(info |)
     endif
 endef

Vagrantfile

@@ -89,7 +89,7 @@ Vagrant.configure(2) do |config|
 
   Examples:
      make planck/rev4:default:dfu
-     make planck:default
+     make planck/rev4:default
 
   EOT
 end