upgrade schiene to 0.20

[JulianKahnert]

Description:

fixes the resolving of delays due to changes at bahn.de (see here).

Checklist:

• The code change is tested and works locally.

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.