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: I649b222bef9d4ac3ab505ec483194f7043b40044

lower-constraints.txt

@@ -1,48 +0,0 @@
-appdirs==1.3.0
-cliff==2.8.0
-cmd2==0.8.0
-coverage==4.5.1
-debtcollector==1.2.0
-deprecation==1.0
-dogpile.cache==0.6.2
-extras==1.0.0
-fixtures==3.0.0
-iso8601==0.1.11
-jmespath==0.9.0
-jsonpatch==1.16
-jsonpointer==1.13
-keystoneauth1==3.4.0
-linecache2==1.0.0
-monotonic==0.6
-munch==2.1.0
-netaddr==0.7.18
-netifaces==0.10.4
-openstacksdk==0.11.2
-os-client-config==1.28.0
-os-service-types==1.2.0
-osc-lib==1.8.0
-oslo.i18n==3.15.3
-oslo.utils==3.33.0
-oslotest==3.3.0
-pbr==3.1.1
-pep8==1.5.7
-prettytable==0.7.2
-pyparsing==2.1.0
-pyperclip==1.5.27
-python-mimeparse==1.6.0
-python-subunit==1.2.0
-pytz==2013.6
-PyYAML==3.12
-requests==2.14.2
-requestsexceptions==1.2.0
-simplejson==3.5.1
-stestr==2.0.0
-stevedore==1.20.0
-testrepository==0.0.18
-testscenarios==0.5.0
-testtools==2.3.0
-traceback2==1.4.0
-unittest2==1.1.0
-wrapt==1.7.0
-pydot==1.4.1
-networkx==2.3

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

@@ -58,9 +58,3 @@ deps =
        -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
        -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -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