Bump rxjava from 2.2.20 to 2.2.21
Bump rxjava from 2.2.20 to 2.2.21

Bumps [rxjava](https://github.com/ReactiveX/RxJava) from 2.2.20 to 2.2.21.
- [Release notes](https://github.com/ReactiveX/RxJava/releases)
- [Changelog](https://github.com/ReactiveX/RxJava/blob/v2.2.21/CHANGES.md)
- [Commits](https://github.com/ReactiveX/RxJava/compare/v2.2.20...v2.2.21)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
Heiner1/AndroidAPS,Heiner1/AndroidAPS,Heiner1/AndroidAPS,Heiner1/AndroidAPS