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: Ibbf905b70d8040cbf2a5f0a35e79c304f247f726

stackforge/python-monascaclient,stackforge/python-monascaclient,openstack/python-monascaclient,sapcc/python-monascaclient,sapcc/python-monascaclient,openstack/python-monascaclient