Bump pytest from 6.2.2 to 6.2.4

Bumps [pytest](https://github.com/pytest-dev/pytest) from 6.2.2 to 6.2.4.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@6.2.2...6.2.4)

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

requirements/dev.txt

@@ -4,14 +4,10 @@
 #
 #    pip-compile --output-file=requirements/dev.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==5.5
     # via pytest-cov
 iniconfig==1.1.1
@@ -26,13 +22,13 @@ pluggy==0.13.1
     # via pytest
 py==1.10.0
     # via pytest
-pylibmc==1.6.1; platform_system != 'Windows'
+pylibmc==1.6.1
     # via -r requirements/dev.in
 pyparsing==2.4.7
     # via packaging
 pytest-cov==2.11.1
     # via -r requirements/dev.in
-pytest==6.2.2
+pytest==6.2.4
     # via
     #   -r requirements/dev.in
     #   pytest-cov