ci: remove py2-rust support
Nobody cares about this very narrow usecase, and py2 support is over by
July 1st. This helps with the CI load, and removes some flakiness.
= Mercurial XXX =
== New Features ==
== Default Format Change ==
These changes affect newly created repositories (or new clones) done with
Mercurial XXX.
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
== Miscellaneous ==