build(deps-dev): bump pytest from 5.4.3 to 6.0.1 in /backend (#580)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.4.3 to 6.0.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@5.4.3...6.0.1)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

backend/requirements-dev.txt

@@ -1,5 +1,5 @@
 fakeredis==1.4.1
 pre-commit==2.6.0
-pytest==5.4.3
+pytest==6.0.1
 pytest-responses==0.4.0
 responses==0.10.15