bug#45175: update gnucash to 4.2

[Leo Famulari]

On Fri, Dec 11, 2020 at 01:23:38PM +0000, Christopher Lam wrote:
> From 2f64bfe91376065e81c4902444cb47e08e3a66b5 Mon Sep 17 00:00:00 2001
> From: Christopher Lam <christopher.lck@gmail.com>
> Date: Fri, 11 Dec 2020 21:20:06 +0800
> Subject: [PATCH] gnucash.scm: update to 4.2

Thank you!

I rewrote the commit message to meet our standards, added a copyright
line for you, and pushed as 6760578c89bfbc32b55f860dc63a0b1513dd95d3.

About the commit message, we write them in the GNU ChangeLog format:

https://guix.gnu.org/manual/en/html_node/Submitting-Patches.html

Basically, we describe changes to the code, organized by file and
variable. The chapter in the GNU coding manual that is linked to from
our Submitting Patches guidelines is instructive when combined with `git
log` of the Guix repo.