build(deps-dev): Bump pytest from 5.3.5 to 5.4.1 in /backend (#460)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.3.5 to 5.4.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@5.3.5...5.4.1)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

backend/requirements-dev.txt

@@ -1,5 +1,5 @@
 fakeredis==1.2.1
 pre-commit==2.2.0
-pytest==5.3.5
+pytest==5.4.1
 pytest-responses==0.4.0
 responses==0.10.12