Drop support for abandoned Briki boards #183

Job	Run time
build (ubuntu-latest, examples/arduino-blink)	2m 6s
build (ubuntu-latest, examples/arduino-external-libs)	1m 49s
build (ubuntu-latest, examples/arduino-internal-libs)	1m 40s
build (ubuntu-latest, examples/arduino-web-thing-led)	46s
build (ubuntu-latest, examples/zephyr-blink)	2m 14s
build (ubuntu-latest, examples/zephyr-drivers-lcd-hd44780)	1m 55s
build (ubuntu-latest, examples/zephyr-subsys-logger)	2m 6s
build (windows-latest, examples/arduino-blink)	4m 37s
build (windows-latest, examples/arduino-external-libs)	3m 58s
build (windows-latest, examples/arduino-internal-libs)	4m 39s
build (windows-latest, examples/arduino-web-thing-led)	2m 10s
build (windows-latest, examples/zephyr-blink)	5m 5s
build (windows-latest, examples/zephyr-drivers-lcd-hd44780)	4m 54s
build (windows-latest, examples/zephyr-subsys-logger)	5m 5s
build (macos-latest, examples/arduino-blink)	2m 53s
build (macos-latest, examples/arduino-external-libs)	2m 47s
build (macos-latest, examples/arduino-internal-libs)	2m 28s
build (macos-latest, examples/arduino-web-thing-led)	1m 12s
build (macos-latest, examples/zephyr-blink)	4m 17s
build (macos-latest, examples/zephyr-drivers-lcd-hd44780)	3m 31s
build (macos-latest, examples/zephyr-subsys-logger)	3m 24s
	1h 3m 36s

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