Make "arc land" prompt on "Changes Planned" revisions more explicit
Make "arc land" prompt on "Changes Planned" revisions more explicit

Summary: Fixes T10233. See PHI231. Users sometimes believe this warning is a bug and/or don't understand how they're supposed to resolve it.

Test Plan: Ran `arc land` on a revision in "Changes Planned", got a sensible prompt. Ran `arc land` on a revision in another non-accepted state, got more or less the old prompt.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T10233

Differential Revision: https://secure.phabricator.com/D18807

Khan/arcanist,phacility/arcanist,codelabs-ch/arcanist,codelabs-ch/arcanist,Khan/arcanist,aik099/arcanist,r4nt/arcanist,phacility/arcanist,aik099/arcanist,codelabs-ch/arcanist,Khan/arcanist,codelabs-ch/arcanist,aik099/arcanist,codelabs-ch/arcanist,phacility/arcanist,r4nt/arcanist,phacility/arcanist,aik099/arcanist,r4nt/arcanist,uber/arcanist,uber/arcanist,r4nt/arcanist,Khan/arcanist,phacility/arcanist,uber/arcanist,uber/arcanist