Remove python-novaclient from requirements.txt

Change I050e92bc5620d6e748cf1d948ef2a52305aa02b5 removed the novaclient
cli tests from tempest, which was the last use of python-novaclient in
tempest. However, it neglected to remove it from the requirements.txt
file. This commit fixes the oversight.

Change-Id: Ib2d321846a79fe7582ea4dc7f80e146963b37d16
1 file changed