cleanup: update references to /help/ that should now be /helptext/
I noticed this only because the WiX build was broken after
2e017696181f. I haven't tested this change with WiX, but it seems
pretty obvious by inspection this should fix it.
Differential Revision: https://phab.mercurial-scm.org/D7472
[workspace]
members = ["hg-core", "hg-direct-ffi", "hg-cpython"]
exclude = ["chg", "hgcli"]