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: I7d734cb7ea9bea06a7065645e6d7028f6cbdff00

.zuul.yaml

@@ -7,7 +7,6 @@
       #NOTE(rpittau): cover tests needs some config changes, we'll enable them
       # in a future patch
       #- openstack-cover-jobs
-      - openstack-lower-constraints-master-branch-jobs
       - openstack-python3-yoga-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

lower-constraints.txt

@@ -1,9 +0,0 @@
-PyMySQL==0.8.0
-PyYAML==3.10
-SQLAlchemy-Utils==0.30.11
-SQLAlchemy==1.2.19
-coverage==4.0
-daemonize==2.5.0
-oslotest==3.2.0
-pbr==2.0.0
-stestr==2.0.0

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.
+
 # 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.

tox.ini

@@ -161,9 +161,3 @@ filename =
   *.py,
   *molteniron,
   *moltenirond-helper
-
-[testenv:lower-constraints]
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt