Bump mock from 4.0.2 to 4.0.3

Bumps [mock](https://github.com/testing-cabal/mock) from 4.0.2 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@4.0.2...4.0.3)

---
updated-dependencies:
- dependency-name: mock
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

requirements.txt

@@ -14,7 +14,7 @@ idna==3.3
 Jinja2==3.0.2
 lxml==4.6.3
 MarkupSafe==2.0.1
-mock==4.0.2
+mock==4.0.3
 multidict==5.2.0
 pycountry==20.7.3
 PyPDF2==1.26.0