Drop lower-constraints.txt and its testing

As discussed in TC PTG[1] and TC resolution[2], 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: I67983c66fc52bfb7d083408b28ffd75d2c580527

lower-constraints.txt

@@ -1,43 +0,0 @@
-Babel==2.6.0
-Flask==1.1.0
-PyYAML==5.3.1
-SQLAlchemy==1.2.19
-alembic==1.4.2
-automaton==1.9.0
-bandit==1.1.0
-cliff==3.3.0
-construct==2.9.39
-coverage==4.0
-dogpile.cache==0.9.2
-eventlet==0.26.0
-fixtures==3.0.0
-futurist==1.2.0
-ironic-lib==4.3.0
-jsonpath-rw==1.2.0
-jsonschema==3.2.0
-keystoneauth1==4.2.0
-keystonemiddleware==4.18.0
-netaddr==0.7.18
-openstacksdk==0.40.0
-oslo.concurrency==3.26.0
-oslo.config==6.8.0
-oslo.context==2.22.0
-oslo.db==6.0.0
-oslo.i18n==3.20.0
-oslo.log==4.3.0
-oslo.messaging==5.32.0
-oslo.middleware==3.31.0
-oslo.policy==3.7.0
-oslo.rootwrap==5.8.0
-oslo.serialization==2.25.0
-oslo.service==1.31.0
-oslo.upgradecheck==1.2.0
-oslo.utils==4.5.0
-oslotest==3.2.0
-pbr==3.1.1
-pymemcache==1.2.9
-pytz==2013.6
-stestr==1.0.0
-stevedore==1.20.0
-tenacity==6.2.0
-tooz==2.5.1

zuul.d/project.yaml

@@ -2,7 +2,6 @@
     templates:
       - check-requirements
       - openstack-cover-jobs
-      - openstack-lower-constraints-master-branch-jobs
       - openstack-python3-zed-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3