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: Ib5364b375daba592af39118131670c5d234ec0cb

.zuul.yaml

@@ -1,7 +1,6 @@
 - project:
     templates:
       - check-requirements
-      - openstack-lower-constraints-jobs
       - openstack-python3-yoga-jobs
       - release-notes-jobs-python3
     gate:

lower-constraints.txt

@@ -1,23 +0,0 @@
-coverage==4.0
-ddt==1.2.1
-debtcollector==1.19.0
-eventlet==0.22.0
-netaddr==0.7.18
-openstackdocstheme==2.2.1
-oslo.concurrency==3.29.0
-oslo.config==6.8.0
-oslo.context==2.22.2
-oslo.i18n==3.15.3
-oslo.log==3.36.0
-oslo.serialization==2.21.1
-oslo.utils==4.7.0
-oslotest==3.8.0
-pbr==2.0.0
-PyMI==1.0.0;sys_platform=='win32'
-six==1.12.0
-stestr===2.0.0
-stevedore==1.20.0
-testscenarios==0.4
-testtools==2.2.0
-wmi==0.5;sys_platform=='win32'
-wrapt==1.7.0

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

@@ -59,11 +59,3 @@ extension =
   O301 = checks:assert_ctypes_libs_not_used_directly
   O302 = checks:assert_ctypes_foreign_func_argtypes_defined
 paths = ./os_win/_hacking
-
-
-[testenv:lower-constraints]
-basepython = python3
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt