Update faq.pod6

edit the zef url so that it is recognised by modules.raku.org
remove reference to p6doc, which is not being found there,

doc/Language/faq.pod6

@@ -96,8 +96,7 @@ Some users choose to use L<rakubrew|https://rakubrew.org/>, which allows
 quick installation of multiple versions of Rakudo in parallel.
 
 In either case you will probably need to also install
-L«C<zef>|https://modules.raku.org/dist/zef:github» and
-L«C<p6doc>|https://modules.raku.org/dist/p6doc:github» from the
+L«C<zef>|https://modules.raku.org/dist/zef» from the
 L<ecosystem|https://modules.raku.org/>.
 
 =head2 Where can I find good documentation on Raku?