remove deprecated pytest-runner

See https://github.com/pytest-dev/pytest-runner/#deprecation-notice. We
can call pytest directly instead.

.github/workflows/python.yml

@@ -41,13 +41,11 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -e .
-        python setup.py develop
+        pip install -e '.[test]'
 
     - name: Compile all scripts
       run: python -m compileall -f terminatorlib/ tests/ remotinator terminator
 
     - name: Run tests
       run: |
-        pip install -e '.[test]'
-        xvfb-run -a python setup.py test
+        xvfb-run -a pytest

setup.py

@@ -219,9 +219,6 @@ setup(name=APP_NAME,
           'terminatorlib',
           'terminatorlib.plugins',
       ],
-      setup_requires=[
-          'pytest-runner',
-      ],
       install_requires=[
           'pycairo',
           'configobj',
@@ -229,7 +226,6 @@ setup(name=APP_NAME,
           'pygobject',
           'psutil',
       ],
-      tests_require=test_deps,
       extras_require={'test': test_deps},
       package_data={'terminatorlib': ['preferences.glade', 'layoutlauncher.glade']},
       cmdclass={'build': BuildData, 'install_data': InstallData, 'uninstall': Uninstall},