[PATCH 2 of 2] histedit: dropmissing hint

[timeless]

Mateusz Kwapich wrote:
> + * If you remove a line here THAT COMMIT WILL BE DELETED

"deleted" might not be correct, and I don't think this is the best way
to say what we want.
("line here THAT COMMIT" is a bit of a mess)

"Removing a changeset from the list of changes will result in it being
excluded (deleted) from the rewritten history."

Possibly w/ "deleted" depending on whether or not obsmarkers are being used...

> + * However, if you remove everything, the histedit will be aborted.

I don't think this is worth saying. Alternatively, we could suggest
this advice even if !dropmissing. For now, i'd suggest omitting it.