Update responses requirement from ~=0.19.0 to ~=0.20.0

Updates the requirements on [responses](https://github.com/getsentry/responses) to permit the latest version.
- [Release notes](https://github.com/getsentry/responses/releases)
- [Changelog](https://github.com/getsentry/responses/blob/master/CHANGES)
- [Commits](getsentry/responses@0.19.0...0.20.0)

---
updated-dependencies:
- dependency-name: responses
  dependency-type: direct:development
...

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

requirements-dev.txt

@@ -1,4 +1,4 @@
-responses~=0.19.0
+responses~=0.20.0
 pre-commit
 isort
 pytest