`removal` newsfragments do not show in history

[richardsheridan]

We have several removals pending and I was directed to make one in #2841, but removal is not a valid towncrier type right now. Do we want to rename newsfragments, or add removal and remove deprecated, or maybe there is a way to alias them?

[A5rocks]

Yeah I noticed this and my conclusion is we should add a new removal type that mirrors deprecated. If you check the readme in the newsfragments folder it mentions both are for different things after all.

[oremanj]

My suggestion of removal in the cancellable -> abandon_on_cancel diff was incorrect; that should have been deprecated. I got confused by the other removal newsfragments, which I agree that we should support.