Remove usage of changectx
The method has been removed in changeset 836867586b83 of Mercurial.
usr/share/mercurial-server
usr/share/mercurial-server/init
usr/share/mercurial-server/mercurialserver
usr/share/doc/mercurial-server
etc/mercurial-server
etc/mercurial-server/remote-hgrc.d
etc/mercurial-server/keys
etc/mercurial-server/keys/root
etc/mercurial-server/keys/users