SW: drop firmware-ath9k-htc (files provided by firmware-atheros)

SW: drop firmware-ath9k-htc (files provided by firmware-atheros)

firmware-ath9k-htc (~161 kB installed size, "firmware for AR7010 and
AR9271 USB wireless adapter") was and still is available from Debian
main. firmware-ath9k-htc in stable/bullseye ships the following firmware
files:

  % dpkg -L firmware-ath9k-htc | grep /htc
  /lib/firmware/ath9k_htc/htc_7010-1.dev.0.fw
  /lib/firmware/ath9k_htc/htc_9271-1.dev.0.fw

  % rmadison firmware-ath9k-htc
  firmware-ath9k-htc | 1.4.0-97-g75b3e59+dfsg-3     | oldstable  | all
  firmware-ath9k-htc | 1.4.0-106-gc583009+dfsg1-1   | stable     | all
  firmware-ath9k-htc | 1.4.0-108-gd856466+dfsg1-1   | testing    | all
  firmware-ath9k-htc | 1.4.0-108-gd856466+dfsg1-1.2 | unstable   | all

firmware-atheros (available from non-free until and including bullseye
and starting with bookworm from non-free-firmware, ~31MB installed size
in bullseye and ~62MB in unstable) ships the following ath* related
firmware files since loong time (according to firmware-nonfree.git since
its git rev 7dd7dfd2 which is included as of version 0.28 AKA around
Debian squeeze):

  % dpkg -L firmware-atheros | grep -e htc_7 -e htc_9
  /lib/firmware/ath9k_htc/htc_7010-1.4.0.fw
  /lib/firmware/ath9k_htc/htc_9271-1.4.0.fw
  /lib/firmware/htc_7010.fw
  /lib/firmware/htc_9271.fw

  % rmadison firmware-atheros
  firmware-atheros | 0.43               | oldoldoldstable/non-free    | all
  firmware-atheros | 20161130-5         | oldoldstable/non-free       | all
  firmware-atheros | 20190114-2~bpo9+1  | stretch-backports/non-free  | all
  firmware-atheros | 20190114-2         | oldstable/non-free          | all
  firmware-atheros | 20210315-3~bpo10+1 | buster-backports/non-free   | all
  firmware-atheros | 20210315-3         | stable/non-free             | all
  firmware-atheros | 20210818-1~bpo11+1 | bullseye-backports/non-free | all
  firmware-atheros | 20230117-2         | testing/non-free-firmware   | all
  firmware-atheros | 20230210-1         | unstable/non-free-firmware  | all

Nowadays firmware-ath9k-htc (1.4.0-108-gd856466+dfsg1-1.2 as present in
Debian/unstable) also ships the same file names (see https://bugs.debian.org/1031186
AKA "firmware-ath9k-htc: rename to stable version"):

  % dpkg -L firmware-ath9k-htc | grep /htc
  /lib/firmware/ath9k_htc/htc_7010-1.4.0.fw
  /lib/firmware/ath9k_htc/htc_9271-1.4.0.fw

So firmware-ath9k-htc uses:

  Replaces: firmware-atheros (<= 20230210-1)
  Breaks: firmware-atheros (<= 20230210-1)

and we can no longer ship both firmware-ath9k-htc and firmware-atheros,
so drop firmware-ath9k-htc from GRMLBASE.

FTR, /etc/modprobe.d/ath9k_htc.conf (shipped by firmware-ath9k-htc) included:

  options ath9k_htc use_dev_fw=1