Referencing old chlog on in help

[jubalh]

Reported by Klemens Nanni via mailinglist:

Running on

	$ uname -smr
	OpenBSD 6.8 amd64

	$ profanity --version
	Profanity, version 0.10.0
	Copyright (C) 2012 - 2019 James Booth <boothj5web at gmail.com>.
	Copyright (C) 2019 - 2021 Michael Vetter <jubalh at iodoru.org>.
	License GPLv3+: GNU GPL version 3 or later <https://www.gnu.org/licenses/gpl.html>

	This is free software; you are free to change and redistribute it.
	There is NO WARRANTY, to the extent permitted by law.

	Build information:
	XMPP library: libmesode
	Desktop notification support: Disabled
	OTR support: Enabled (libotr 4.1.1)
	PGP support: Enabled (libgpgme 1.14.0)
	OMEMO support: Enabled
	C plugins: Enabled
	Python plugins: Enabled (3.8.7)
	GTK icons: Disabled

I noticed the following while configuring OMEMO:

	/omemo log on
	11:06:38 - OMEMO messages will be logged as plaintext.
	11:06:38 - Chat logging is currently disabled, use '/chlog on' to enable.

	/chlog on
	11:06:40 - Unknown command: /chlog on

	/help chlog
	11:06:40 - No such command.