Remove setup.py test infra - now deprecated

pypa/setuptools#1878

requirements_dev.txt

@@ -5,6 +5,4 @@ flake8==3.7.8
 coverage==4.5.4
 Sphinx==1.8.5
 twine==1.14.0
-
 pytest==4.6.5
-pytest-runner==5.1

setup.py

@@ -15,15 +15,6 @@
     'publicsuffix',
 ]
 
-setup_requirements = [
-    'pytest-runner',
-]
-
-test_requirements = [
-    'pytest>=3', 
-    'pytest-flake8', 
-]
-
 setup(
     author="Sarah Bird",
     author_email='[email protected]',
@@ -47,9 +38,6 @@
     keywords='domain_utils',
     name='domain_utils',
     packages=find_packages(include=['domain_utils', 'domain_utils.*']),
-    setup_requires=setup_requirements,
-    test_suite='tests',
-    tests_require=test_requirements,
     url='https://github.com/mozilla/domain_utils',
     version='0.4.0',
     zip_safe=False,