Travis: Remove flake8 and black.

They run in Github Actions.

Author: methane

.travis.yml

@@ -60,20 +60,6 @@ jobs:
       script:
         - cd django-${DJANGO_VERSION}/tests/
         - ./runtests.py --parallel=2 --settings=test_mysql
-    - name: flake8
-      python: "3.8"
-      install:
-        - pip install -U pip
-        - pip install flake8
-      script:
-        - flake8 --ignore=E203,E501,W503 --max-line-length=88 .
-    - name: black
-      python: "3.8"
-      install:
-        - pip install -U pip
-        - pip install black
-      script:
-        - black --check --exclude=doc/ .
     #- &django_3_0
     #  <<: *django_2_2
     #  name: "Django 3.0 test (Python 3.8)"