remove python 2.6 trove classifier
remove python 2.6 trove classifier

OpenStack projects are no longer being tested under Python 2.6, so
remove the trove classifier implying that this project supports 2.6.

Change-Id: Ieb5c4161d1f230c827d40eac9218392b425f321a

stackforge/poppy,openstack/poppy,openstack/poppy,stackforge/poppy,stackforge/poppy,openstack/poppy