histedit: use rewriteutil.precheck() instead of reimplementing it We have had this nice utility since 490df753894d (rewriteutil: add a precheck function to check if revs can be rewritten, 2017-11-24). We got two callers soon thereafter, in 98f97eb20597 (rewriteutil: use precheck() in uncommit and amend commands, 2017-11-28). It's about time we use it in other places. rewriteutil.precheck() looks unfortunate for i18n (it seems to rely on an English verb for the action making sense in other languages), but hopefully not bad enough that we should avoid using it. Differential Revision: https://phab.mercurial-scm.org/D7684