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: I775420251d6e47f60c4a266b4013be84a52378da
(cherry picked from commit 937a03b)

Author: gmaanos

.zuul.yaml

@@ -120,7 +120,6 @@
 - project:
     queue: cloudkitty
     templates:
-      - openstack-lower-constraints-jobs
       - check-requirements
       - openstack-cover-jobs
       - openstack-python3-yoga-jobs

lower-constraints.txt

@@ -1,6 +1,11 @@
+# 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.
+
 # 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.
+
 pbr>=5.5.1 # Apache-2.0
 alembic>=1.4.3 # MIT
 keystonemiddleware>=9.1.0 # Apache-2.0

requirements.txt

@@ -97,9 +97,3 @@ paths = ./cloudkitty/hacking
 [testenv:releasenotes]
 deps = {[testenv:docs]deps}
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
-
-[testenv:lower-constraints]
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt