Bump flower from 0.9.3 to 1.2.0

Bumps [flower](https://github.com/mher/flower) from 0.9.3 to 1.2.0.
- [Release notes](https://github.com/mher/flower/releases)
- [Commits](https://github.com/mher/flower/compare/v0.9.3...v1.2.0)

---
updated-dependencies:
- dependency-name: flower
  dependency-type: direct:production
...

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

requirements.txt

@@ -49,7 +49,7 @@ django-timezone-field==3.0
 djangorestframework==3.9.2
 docutils==0.14
 dramatiq==1.5.0
-flower==0.9.3
+flower==1.2.0
 funcsigs==1.0.0
 future==0.16.0
 gevent==1.4.0