Drop lower constraints testing

The lower constraints testing was removed from all repositories managed
by the Oslo project. This change removes that test from cookiecutter
as well.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2020-December/019390.html

Change-Id: I22b98e7235c221e44c2b13a25f30f3bd18e53ba5

oslo.{{cookiecutter.module_name}}/lower-constraints.txt

@@ -1,8 +0,0 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
-
-hacking==2.0.0
-mypy==0.720
-oslotest==1.5.1
-reno==2.5.0

oslo.{{cookiecutter.module_name}}/tox.ini

@@ -12,11 +12,6 @@ deps =
     -r{toxinidir}/test-requirements.txt
 commands = stestr run --slowest {posargs}
 
-[testenv:lower-constraints]
-deps = -c{toxinidir}/lower-constraints.txt
-       -r{toxinidir}/requirements.txt
-       -r{toxinidir}/test-requirements.txt
-
 [testenv:pep8]
 commands = flake8 {posargs}
 

tools/test_tox_targets.sh

@@ -30,4 +30,4 @@ def test_api():
     pass
 EOF
 
-tox -e pep8,py36,docs,lower-constraints,cover,releasenotes
+tox -e pep8,py36,docs,cover,releasenotes