head-revs: stop calling headrevsfiltered
The `headrevs` method have been accepting filter since Mercurial 3.2ยน. I guess
we can rely on it for now.
(except the Rust extension that just gained this capability, but it has it now)
.. Common link and substitution definitions.
.. |hg(1)| replace:: **hg**\ (1)
.. _hg(1): hg.1.html
.. |hgrc(5)| replace:: **hgrc**\ (5)
.. _hgrc(5): hgrc.5.html
.. |hgignore(5)| replace:: **hgignore**\ (5)
.. _hgignore(5): hgignore.5.html