Missing firmware for i915

A recent update (I'm not sure which, sorry) has resulted in systems with the i915 module loaded outputting errors when updating initramfs.

I reproduced this on a clean Ubuntu 18.04 VM with HWE kernel and all updates applied by:
1. sudo modprobe i915
2. sudo apt-get install linux-firmware --reinstall

This resulted in the following errors:
update-initramfs: Generating /boot/initrd.img-5.4.0-42-generic
W: Possible missing firmware /lib/firmware/i915/tgl_dmc_ver2_04.bin for module i915
W: Possible missing firmware /lib/firmware/i915/skl_guc_33.0.0.bin for module i915
W: Possible missing firmware /lib/firmware/i915/bxt_guc_33.0.0.bin for module i915
W: Possible missing firmware /lib/firmware/i915/kbl_guc_33.0.0.bin for module i915
W: Possible missing firmware /lib/firmware/i915/glk_guc_33.0.0.bin for module i915
W: Possible missing firmware /lib/firmware/i915/kbl_guc_33.0.0.bin for module i915
W: Possible missing firmware /lib/firmware/i915/icl_guc_33.0.0.bin for module i915

It appears that /lib/firmware/i915 contains 32.0.3 versions of those components, rather than 33.0.0

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-firmware 1.173.19
ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
CurrentDesktop: LXDE
Date: Sat Aug 8 12:40:36 2020
Dependencies:

EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-18 (1938 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
PackageArchitecture: all
SourcePackage: linux-firmware
UpgradeStatus: Upgraded to bionic on 2020-02-15 (174 days ago)