tests/test-locale.t

heptapod-ci: remove useless mentions of Python 3

Now that we don't have Python 2 jobs, we can go with shorter names.

Differential Revision: https://phab.mercurial-scm.org/D12354

  $ LANG=nonexistent LC_ALL=nonexistent LANGUAGE=nonexistent hg version -q
  Mercurial Distributed SCM (version *) (glob)