Remove deprecated allow_tenant_isolation option

allow_tenant_isolation option of auth and compute groups has been
deprecated over 3 years since I78a4884e980ef7d0103639cb3792a54c69fb7761.
So we have spended much enough time for removing them, this patch does.

Change-Id: I0b0a5e16a5e3785579f95f75fa149b311d918e8c
diff --git a/tempest/config.py b/tempest/config.py
index 1fb5c8e..cc0ba34 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -61,11 +61,7 @@
                      "users. This option requires that OpenStack Identity "
                      "API admin credentials are known. If false, isolated "
                      "test cases and parallel execution, can still be "
-                     "achieved configuring a list of test accounts",
-                deprecated_opts=[cfg.DeprecatedOpt('allow_tenant_isolation',
-                                                   group='auth'),
-                                 cfg.DeprecatedOpt('allow_tenant_isolation',
-                                                   group='compute')]),
+                     "achieved configuring a list of test accounts"),
     cfg.ListOpt('tempest_roles',
                 help="Roles to assign to all users created by tempest",
                 default=[]),