manual: reviewing contributions nixos -> nixpkgs (#20626)

doc/manual.xml

@@ -20,6 +20,7 @@
   <xi:include href="package-notes.xml" />
   <xi:include href="coding-conventions.xml" />
   <xi:include href="submitting-changes.xml" />
+  <xi:include href="reviewing-contributions.xml" />
   <xi:include href="contributing.xml" />
 
 </book>

nixos/doc/manual/development/development.xml

@@ -18,7 +18,6 @@ NixOS.</para>
 <xi:include href="building-nixos.xml" />
 <xi:include href="nixos-tests.xml" />
 <xi:include href="testing-installer.xml" />
-<xi:include href="reviewing-contributions.xml" />
 <xi:include href="releases.xml" />
 
 </part>