Remove Babel from requirements.txt
Remove Babel from requirements.txt

Babel wasn't used at all and creates a version conflict under
some circumstances.

Change-Id: I48120d546d139cc686155b5144a5ba36f9201943

jianghuaw/nova,openstack/nova,jianghuaw/nova,klmitch/nova,gooddata/openstack-nova,mikalstill/nova,gooddata/openstack-nova,openstack/nova,rahulunair/nova,klmitch/nova,klmitch/nova,mikalstill/nova,mahak/nova,klmitch/nova,phenoxim/nova,rahulunair/nova,vmturbo/nova,Juniper/nova,mahak/nova,Juniper/nova,mahak/nova,vmturbo/nova,jianghuaw/nova,jianghuaw/nova,vmturbo/nova,Juniper/nova,rahulunair/nova,openstack/nova,Juniper/nova,gooddata/openstack-nova,gooddata/openstack-nova,vmturbo/nova,mikalstill/nova,phenoxim/nova