[WIP] Edited replies don't change mention state

Created by: CatThingy

Summary

Fixes #833.

Details

Implemented as discussed in https://github.com/DSharpPlus/DSharpPlus/issues/833#issuecomment-817133735 and https://github.com/DSharpPlus/DSharpPlus/issues/833#issuecomment-817133953.