update ansible version

Update the version of ansible because ansible-core was updated to 2.13-2.14

[1] https://review.opendev.org/c/openstack/kolla-ansible/+/883525

Change-Id: If3223fe17f9e480a9782c2696ed945d24a8dae5e

test-requirements.txt

@@ -5,4 +5,4 @@ coverage!=4.4,>=4.0 # Apache-2.0
 docker>=2.4.2 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 stestr>=2.0.0 # Apache-2.0
-ansible>=4,<6 # GPLv3
+ansible>=6,<8 # GPLv3