variables: clarify the use of NOACT to avoid any confusion

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

.gitlab-ci.yml

@@ -15,7 +15,8 @@ variables:
       - checking
   NOACT:
     description: |
-      Use this to variable to avoid performing changes (dry mode)
+      Use this variable to avoid performing changes (dry mode):
+      1 is for a dry run (no changes applied), 0 is for applying changes.
     value: "1"
     options:
       - "1"