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)

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

requirements/dev.txt

@@ -4,18 +4,16 @@
 #
 #    pip-compile --output-file=requirements/dev-py3.txt requirements/dev.in
 #
-atomicwrites==1.4.0       # via pytest
 attrs==20.3.0             # via pytest
 click==7.1.2              # via pip-tools
-colorama==0.4.4           # via pytest
 coverage==5.3             # via pytest-cov
 iniconfig==1.1.1          # via pytest
-mock==4.0.2               # via -r requirements/dev.in
+mock==4.0.3               # via -r requirements/dev.in
 packaging==20.4           # via pytest
 pip-tools==5.3.1          # via -r requirements/dev.in
 pluggy==0.13.1            # via pytest
 py==1.9.0                 # via pytest
-pylibmc==1.6.1; platform_system != 'Windows'            # via -r requirements/dev.in
+pylibmc==1.6.1            # via -r requirements/dev.in
 pyparsing==2.4.7          # via packaging
 pytest-cov==2.10.1        # via -r requirements/dev.in
 pytest==6.1.2             # via -r requirements/dev.in, pytest-cov