BUG #17039: Won't Upgrade - Repo Error

The following bug has been logged on the website:

Bug reference:      17039
Logged by:          KitchM
Email address:      kitchm@tutanota.com
PostgreSQL version: 11.12
Operating system:   Raspian 10
Description:

Raspian Linux 10 with postgres (PostgreSQL) 11.12 (Raspian
11.12-0+deb10u1).

Sudo apt update stated that there was one upgrade available, and then said:
N: Skipping acquire of configured file 'main/binary-armhf/Packages' as
repository 'http://apt.postgresql.org/pub/repos/apt buster-pgdg InRelease'
doesn't support architecture 'armhf'

Sudo apt list --upgradable shows:
linux-libc-dev/testing 1:1.20210430-2 armhf [upgradable from:
4.18.120-2+rpi1]
N: There is 1 additional version.  Please use the '-a' switch to see it
Doing so shows same line plus new line:
linux-libc-dev/stable.now 4.18.20-2+rpi1 armhf [installed, upgradable to:
1:1.20210430-2]