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: Ifbc383f6d4c858189cee55e67b4d4274d9c3358a

Author: gmaanos

.zuul.yaml

@@ -608,7 +608,6 @@
       - check-requirements
       - integrated-gate-compute
       - openstack-cover-jobs
-      - openstack-lower-constraints-jobs
       - openstack-python3-zed-jobs
       - openstack-python3-zed-jobs-arm64
       - periodic-stable-jobs

lower-constraints.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>=5.8.0 # Apache-2.0
 SQLAlchemy>=1.4.13 # MIT
 decorator>=4.1.0 # BSD

requirements.txt

@@ -391,10 +391,3 @@ deps = bindep
 extras =
 commands =
   bindep test
-
-[testenv:lower-constraints]
-usedevelop = False
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt