Drop lower-constraints.txt and its testing

As discussed in TC PTG[1] and TC resolution[2], we are
dropping the lower-constraints.txt file and its testing.
We will keep lower bounds in the requirements.txt file but
with a note that these are not tested lower bounds and we
try our best to keep them updated.

[1] https://etherpad.opendev.org/p/tc-zed-ptg#L326
[2] https://governance.openstack.org/tc/resolutions/20220414-drop-lower-constraints.html#proposal

Change-Id: Iddc2ee3d59b3fac20f6df80b2baf3be439b24128

.zuul.yaml

@@ -83,7 +83,6 @@
     templates:
       - check-requirements
       - openstack-cover-jobs
-      - openstack-lower-constraints-master-branch-jobs
       - openstack-python3-zed-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

lower-constraints.txt

@@ -1,10 +0,0 @@
-Flask==1.0.0
-cliff==3.3.0
-coverage==4.0
-dogpile.cache==0.9.2
-oslo.messaging==9.4.0
-oslotest==3.2.0
-pbr==3.1.1
-prometheus_client==0.6.0
-stestr==2.0.0
-stevedore==1.20.0

requirements.txt

@@ -1,3 +1,7 @@
+# Requirements lower bounds listed here are our best effort to keep them up to
+# date but we do not test them so no guarantee of having them all correct. If
+# you find any incorrect lower bounds, let us know or propose a fix.
+
 pbr>=3.1.1 # Apache-2.0
 stevedore>=1.20.0 # Apache-2.0
 oslo.messaging>=9.4.0 # Apache-2.0

tox.ini

@@ -75,9 +75,3 @@ application-import-names = ironic_prometheus_exporter
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 import-order-style = pep8
 show-source = True
-
-[testenv:lower-constraints]
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt