Previously, the documentation comment on GitHub would be removed and
then recreated which creates notification emails and to some feels like
it's polluting their GitHub inbox.

Here, we change this behavior so that only the initial build of the
documentation causes such a notification. Further updates to the
documentation, do update the links in the comment but do not trigger a
notification.

This is meant as an alternative to sagemath#37387. See sagemath#37739 for futher ideas
about a smarter behavior here.