Don't use upper-constraints with molecule

We were always using the upper-constraints when creating tox
environments, however there is currently an issue with molecule and
openstack upper-constraints that is preventing it from being used.
Until molecule can be fixed to work with openstack upper-constraints,
lets drop this configuration. We are already adding the constraints to
the doc and release notes jobs.

https://github.com/ansible-community/molecule/pull/3244

Change-Id: I91ebaa059dc2451bba739a0a2de917e2f3c2aa21
Related-Bug: #1942704

tox.ini

@@ -5,7 +5,7 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = python3 -m pip install -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master} {opts} {packages}
+install_command = python3 -m pip install {opts} {packages}
 passenv = *
 setenv =
   ANSIBLE_ACTION_PLUGINS={toxinidir}/tripleo_ansible/roles.galaxy/config_template/action:{toxinidir}/tripleo_ansible/ansible_plugins/action
@@ -50,8 +50,6 @@ commands = bindep test
 skipsdist = True
 skip_install = True
 sitepackages = False
-setenv =
-  TOX_CONSTRAINTS_FILE=file:///dev/null
 deps =
     pre-commit
     virtualenv