Remove allow_failure from gitlab linting rules

.gitlab-ci.yml

@@ -38,13 +38,11 @@ run_black:
   stage: lint
   script:
     - tox -e black
-  allow_failure: true
 
 run_flake8:
   stage: lint
   script:
     - tox -e pep8
-  allow_failure: true
 
 run_pylint:
   stage: lint