Remove ET realtime override code

[Bartosz-Kruba]

Summary

Ensure that OTP does not override times from SIRI ET messages.

Issue

#3909

Unit tests

This is a minor fix. No unit tests needed.

Code style

Following code style.

Documentation

This is a minor fix. No documentation needed.

[t2gran]

I assigned @lassetyr and @hannesj to review this - I am not able to tell if this is correct or not.

[hannesj]

This is causing problems for us, as none of the last stops have a realtimeDepartureTime, meaning that the trip update is skipped, if the last stop arrival has any delay.