Dropping lower constraints testing

We facing errors related to the new pip resolver, this
topic was discussed on the ML and QA team proposed to
to test lower-constraints [1].

I propose to drop this test because the complexity and recurring pain needed
to maintain that now exceeds the benefits provided by this mechanismes.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2020-December/019390.html

Change-Id: I16f5e1dd04ce1d863912dab11e765efb8c85c724

.zuul.yaml

@@ -1,6 +1,5 @@
 - project:
     templates:
-      - openstack-lower-constraints-jobs-horizon
       - check-requirements
       - horizon-non-primary-django-jobs
       - horizon-nodejs10-jobs

lower-constraints.txt

@@ -1,134 +0,0 @@
-alabaster==0.7.10
-appdirs==1.4.3
-asn1crypto==0.24.0
-Babel==2.3.4
-certifi==2018.1.18
-cffi==1.14
-chardet==3.0.4
-cliff==2.11.0
-cmd2==0.8.1
-colorama==0.3.9
-contextlib2==0.5.5
-coverage==4.0
-cryptography==2.1.4
-debtcollector==1.19.0
-decorator==4.4.1
-deprecation==2.0
-django-appconf==1.0.2
-django-babel==0.6.2
-django-compressor==2.2
-django-pyscss==2.0.2
-Django==2.2
-docutils==0.14
-dogpile.cache==0.6.5
-dulwich==0.19.0
-extras==1.0.0
-fasteners==0.14.1
-fixtures==3.0.0
-futurist==1.6.0
-hacking==3.0.1
-horizon==17.1.0
-idna==2.6
-imagesize==1.0.0
-iso8601==0.1.12
-Jinja2==2.10
-jmespath==0.9.3
-jsonpatch==1.21
-jsonpointer==2.0
-jsonschema==2.6.0
-keystoneauth1==3.18.0
-linecache2==1.0.0
-MarkupSafe==1.0
-mccabe==0.6.1
-monotonic==1.4
-msgpack==0.5.6
-munch==2.2.0
-netaddr==0.7.19
-netifaces==0.10.6
-nodeenv==0.9.4
-openstacksdk==0.12.0
-os-client-config==1.29.0
-os-service-types==1.7.0
-osc-lib==1.10.0
-oslo.concurrency==3.26.0
-oslo.config==5.2.0
-oslo.context==2.20.0
-oslo.i18n==3.20.0
-oslo.log==3.37.0
-oslo.policy==1.34.0
-oslo.serialization==2.25.0
-oslo.utils==3.36.0
-osprofiler==2.3.0
-packaging==17.1
-pbr==2.0.0
-pep8==1.5.7
-Pint==0.8.1
-prettytable==0.7.2
-pycparser==2.18
-pyflakes==2.1.0
-Pygments==2.2.0
-pyinotify==0.9.6
-pymongo==3.6.1
-pyOpenSSL==17.5.0
-pyparsing==2.2.0
-pyperclip==1.6.0
-pyScss==1.3.7
-python-cinderclient==5.0.0
-python-dateutil==2.7.0
-python-glanceclient==2.9.1
-python-keystoneclient==3.22.0
-python-mimeparse==1.6.0
-python-neutronclient==6.7.0
-python-novaclient==10.1.0
-python-swiftclient==3.5.0
-python-zaqarclient==1.0.0
-pytz==2018.3
-PyYAML==3.12
-rcssmin==1.0.6
-requests==2.18.4
-requestsexceptions==1.4.0
-rfc3986==1.1.0
-rjsmin==1.0.12
-selenium==2.50.1
-semantic-version==2.6.0
-simplejson==3.13.2
-six==1.11.0
-snowballstemmer==1.2.1
-stevedore==1.28.0
-termcolor==1.1.0
-testtools==2.2.0
-traceback2==1.4.0
-unittest2==1.1.0
-urllib3==1.22
-warlock==1.3.0
-WebOb==1.7.4
-wrapt==1.10.11
-XStatic-Angular-Bootstrap==2.2.0.0
-XStatic-Angular-FileUpload==12.0.4.0
-XStatic-Angular-Gettext==2.3.8.0
-XStatic-Angular-lrdragndrop==1.0.2.2
-XStatic-Angular-Schema-Form==0.8.13.0
-XStatic-Angular==1.5.8.0
-XStatic-Bootstrap-Datepicker==1.3.1.0
-XStatic-Bootstrap-SCSS==3.3.7.1
-XStatic-bootswatch==3.3.7.0
-XStatic-D3==3.5.17.0
-XStatic-Font-Awesome==4.7.0.0
-XStatic-Hogan==2.0.0.2
-XStatic-Jasmine==2.4.1.1
-XStatic-JQuery-Migrate==1.2.1.1
-XStatic-jquery-ui==1.12.0.1
-XStatic-JQuery.quicksearch==2.0.3.1
-XStatic-JQuery.TableSorter==2.14.5.1
-XStatic-jQuery==1.10.2.1
-XStatic-JSEncrypt==2.3.1.1
-XStatic-mdi==1.4.57.0
-XStatic-objectpath==1.2.1.0
-XStatic-Rickshaw==1.5.0.0
-XStatic-roboto-fontface==0.5.0.0
-XStatic-smart-table==1.4.13.2
-XStatic-Spin==1.2.5.2
-XStatic-term.js==0.0.7.0
-XStatic-tv4==1.2.7.0
-XStatic==1.0.1
-xvfbwrapper==0.1.3

tox.ini

@@ -100,16 +100,4 @@ deps =
 commands =
   sphinx-build -a -E -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
-
-[testenv:lower-constraints-local]
-deps =
-  {[testenv:lower-constraints]deps}
-commands =
-  {[testenv:hz-local]commands}
-  {[testenv]commands}