Revert "Run test_port_security_macspoofing_port slow tests serially"

This reverts commit 33e4e24df59605a9e2187f410f470a11d0549c8f.

Reason for revert: Test fixed with [1].
[1] https://review.opendev.org/c/openstack/tempest/+/889713

Change-Id: Ied75aa4c3332a99bc10bcb65d4624a5cafd56f8b
1 file changed