side-data: drop the associated config and requirements
This is no longer and extensions of revlog v1, but a part of revlog v2. We no
longer needs independent config and requirement management for that.
Differential Revision: https://phab.mercurial-scm.org/D10620
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL