remove pytest plugins

setup.cfg

@@ -6,5 +6,4 @@ build-dir = docs/_build
 test = pytest
 
 [tool:pytest]
-addopts = --cov=weasyprint --flake8 --isort
 norecursedirs = dist .cache .git build *.egg-info .eggs venv

setup.py

@@ -75,10 +75,10 @@ setup(
     setup_requires=pytest_runner,
     test_suite='weasyprint.tests',
     tests_require=[
-        'pytest-runner', 'pytest-cov', 'pytest-flake8', 'pytest-isort'],
+        'pytest-runner'],
     extras_require={
         'test': [
-            'pytest-runner', 'pytest-cov', 'pytest-flake8', 'pytest-isort'],
+            'pytest-runner'],
         ':python_version < "3.0"': ['CairoSVG >= 1.0.20, < 2.0.0'],
         ':python_version >= "3.0"': ['CairoSVG >= 1.0.20']},
     entry_points={