Remove Babel as requirement
Remove Babel as requirement

This repo does not use Babel as requirement. See also
http://lists.openstack.org/pipermail/openstack-discuss/2020-April/014227.html

Change I8636e7c86c6c5c608429fab88e181108ae615db9 added it temporarily,
it's time to remove it again.

Leave it in lower-constraints in case dependencies pull it in.

Change-Id: I66bfedcbe30c89a65355e5ab1db6996640d2bfcf

mahak/keystone,mahak/keystone,openstack/keystone,mahak/keystone,openstack/keystone,openstack/keystone