Privacy policy: rewrite introduction and remove unnecessary subsection

The main change is that the scope of the policy is specified explicitly,
using the archlinux.org domain seemed like the best identificator.

privacy-policy.md

 # Privacy Policy for Arch Linux
 
-## Scope of this notice
+This policy describes how Arch Linux collects, uses, protects and discloses user information collected by Arch Linux services, and provides information about the choices you have regarding the ways in which your personal information is manipulated.
 
-This Privacy Policy is intended to describe Arch Linux's privacy practices and provide information about the choices you have regarding the ways in which information collected by Arch Linux is used and disclosed. For convenience, Arch Linux is referred to in this document as "Arch".
+The scope of this privacy policy extends to all public as well as internal services operated by Arch Linux, including in particular all web services provided on the `archlinux.org` domain and its subdomains.
+
+For convenience, Arch Linux is referred to in this document as "Arch".
 
 ## Our commitment to privacy