[tutorial 022] A variable in "shorthand" mode

Transform it in "shorthand" mode.

In this notation we can only define:

- name
- default value (so deduct the type)
- description

firefox/20-manual.yml

@@ -1,6 +1,4 @@
 ---
 manual:
 
-  use_for_https:
-    description: Also use this proxy for HTTPS
-    default: true
+  use_for_https: true  # Also use this proxy for HTTPS