Be consistent in the documentation

The documentation for the `state` field is not very clear.

It says possible values are "installed, uninstalled" and default value is "present"
The examples below alow uses `present` and `absent`.

This patch uses "absent" and "present" instead of "installed" and "uninstalled"

Moreover, this is consistent with other packaging modules, like homebrew itself

lib/ansible/modules/extras/packaging/os/homebrew_cask.py

@@ -32,7 +32,7 @@ options:
     state:
         description:
             - state of the cask
-        choices: [ 'installed', 'uninstalled' ]
+        choices: [ 'present', 'absent' ]
         required: false
         default: present
 '''