build(deps-dev): bump responses from 0.12.1 to 0.13.3 in /backend

Bumps [responses](https://github.com/getsentry/responses) from 0.12.1 to 0.13.3.
- [Release notes](https://github.com/getsentry/responses/releases)
- [Changelog](https://github.com/getsentry/responses/blob/master/CHANGES)
- [Commits](getsentry/responses@0.12.1...0.13.3)

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

Author: dependabot[bot]

backend/requirements-dev.txt

@@ -2,4 +2,4 @@ fakeredis==1.5.0
 pre-commit==2.11.1
 pytest==6.2.2
 pytest-responses==0.4.0
-responses==0.12.1
+responses==0.13.3