helptext: update first hg version when share-safe will be released
I authored the patch which added the helptext before 5.6 release hoping that my
patches will make it. However they didn't before the release and were pushed
after the release only.
Differential Revision: https://phab.mercurial-scm.org/D9410
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true