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
#require black
$ cd $RUNTESTDIR/..
$ black --config=black.toml --check --diff `hg files 'set:(**.py + grep("^#!.*python")) - mercurial/thirdparty/** - "contrib/python-zstandard/**"'`