build(deps-dev): bump pytest from 6.2.2 to 6.2.4 in /backend

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[bot] <support@github.com>

Author: dependabot[bot]

backend/requirements-dev.txt

@@ -1,5 +1,5 @@
 fakeredis==1.5.0
 pre-commit==2.11.1
-pytest==6.2.2
+pytest==6.2.4
 pytest-responses==0.4.0
 responses==0.12.1