Bump mock from 3.0.5 to 4.0.3

Bumps [mock](https://github.com/testing-cabal/mock) from 3.0.5 to 4.0.3.
- [Release notes](https://github.com/testing-cabal/mock/releases)
- [Changelog](https://github.com/testing-cabal/mock/blob/master/CHANGELOG.rst)
- [Commits](testing-cabal/mock@3.0.5...4.0.3)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

setup.py

@@ -55,7 +55,7 @@ def run_tests(self):
     extras_require={
         'Duration': ['python-dateutil>=2.8.0']
     },
-    tests_require=['pytest', 'mock==3.0.5'],
+    tests_require=['pytest', 'mock==4.0.3'],
     entry_points={
         'console_scripts': [
             'pyhocon=pyhocon.tool:main'