setup: Drop tests_require

Current tests have no extra dependencies.
This takes some time before running caucase tests, especially on slower
machines.

setup.py

@@ -49,10 +49,6 @@ setup(
     'pyOpenSSL>=17.1.0', # ...certificate chain validation
     'pem>=17.1.0', # Parse PEM files
   ],
-  tests_require=[
-    'coverage',
-    'pylint',
-  ],
   zip_safe=True,
   entry_points={
     'console_scripts': [