R1:bad645f1ecdd

Remove all application-specific reply handler domains

Summary:
Ref T7199. These were a bad idea which got copy-pasted a bunch.

- There is zero reason to ever set these to different things.
- Unsurprisingly, I don't know of any install which has them set to different things.

Unless I've completely forgotten about it, this option was not motivated by some obscure business need, it was just a bad decision which didn't catch anyone's attention at the time.

We partially remedied the mistake at some…