chore: Recommend the usage of /etc/ instead of /usr/etc/ (#38)

* chore: Recommend the usage of `/etc/` instead of `/usr/etc/`

Related PR:
https://github.com/blue-build/modules/pull/315

* docs: Remove mention of putting files to `/usr/etc/` in recipe

files/system/etc/.gitkeep

@@ -0,0 +1 @@
+

recipes/recipe.yml

@@ -14,9 +14,6 @@ modules:
     files:
       - source: system
         destination: / # copies files/system/* (* means everything inside it) into your image's root folder /
-                       # put configuration files you want in /usr/etc/ inside the image
-                       # while putting files in /etc/ is done on booted system by system administrators.
-                       # read more about this in files module reference.
 
   - type: rpm-ostree
     repos: