Bump pytest-mock from 3.3.1 to 3.4.0 (#5348)

Bumps [pytest-mock](https://github.com/pytest-dev/pytest-mock) from 3.3.1 to 3.4.0.
- [Release notes](https://github.com/pytest-dev/pytest-mock/releases)
- [Changelog](https://github.com/pytest-dev/pytest-mock/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-mock@v3.3.1...v3.4.0)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements/test.txt

@@ -7,7 +7,7 @@ mypy==0.790; implementation_name=="cpython"
 mypy-extensions==0.4.3; implementation_name=="cpython"
 pytest==6.1.2
 pytest-cov==2.10.1
-pytest-mock==3.3.1
+pytest-mock==3.4.0
 re-assert==1.1.0
 setuptools-git==1.2
 trustme==0.6.0; platform_machine!="i686"    # no 32-bit wheels