We are not interested in list of slowest test.

--- cliff-4.8.0/tox.ini.orig
+++ cliff-4.8.0/tox.ini
@@ -10,7 +10,6 @@
   OS_TEST_TIMEOUT=60
 commands =
   stestr run {posargs}
-  stestr slowest
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt