CI: Remove unsupported Django versions from CI pipeline

.gitlab-ci.yml

@@ -6,34 +6,14 @@ before_script:
     - python3.6 -m venv $HOME/tox
     - $HOME/tox/bin/pip install tox
 
-py27-django18:
-    stage: test
-    script: $HOME/tox/bin/tox -e 'py27-django18'
-
-py27-django110:
-    stage: test
-    script: $HOME/tox/bin/tox -e 'py27-django110'
-
 py27-django111:
     stage: test
     script: $HOME/tox/bin/tox -e 'py27-django111'
 
-py36-django18:
-    stage: test
-    script: $HOME/tox/bin/tox -e 'py36-django18'
-
-py36-django110:
-    stage: test
-    script: $HOME/tox/bin/tox -e 'py36-django110'
-
 py36-django111:
     stage: test
     script: $HOME/tox/bin/tox -e 'py36-django111'
 
-py36-django20:
-    stage: test
-    script: $HOME/tox/bin/tox -e 'py36-django20'
-
 py36-django21:
     stage: test
     script: $HOME/tox/bin/tox -e 'py36-django21'