build(deps-dev): bump responses from 0.13.3 to 0.13.4 in /backend (#1053)

Bumps [responses](https://github.com/getsentry/responses) from 0.13.3 to 0.13.4.
- [Release notes](https://github.com/getsentry/responses/releases)
- [Changelog](https://github.com/getsentry/responses/blob/master/CHANGES)
- [Commits](getsentry/responses@0.13.3...0.13.4)

---
updated-dependencies:
- dependency-name: responses
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

backend/requirements-dev.txt

@@ -2,4 +2,4 @@ fakeredis==1.5.2
 pre-commit==2.13.0
 pytest==6.2.4
 pytest-responses==0.5.0
-responses==0.13.3
+responses==0.13.4