Remove usage of changectx
The method has been removed in changeset 836867586b83 of Mercurial.
# Log every push and pull to the servelog
[hooks]
changegroup.aaaaa_servelog = python:mercurialserver.servelog.hook
outgoing.aaaaa_servelog = python:mercurialserver.servelog.hook
pushkey.aaaaa_servelog = python:mercurialserver.servelog.phaseshook