largefiles: remove unused 'rev' parameter from downloadlfiles()
It's no longer used since 83ead8cb0ff2 "largefiles: implement pull
--all-largefiles as a special case of --lfrev."
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.