Drop support for abandoned Briki boards #182

Job	Run time
build (ubuntu-latest, examples/arduino-blink)	2m 7s
build (ubuntu-latest, examples/arduino-briki-internal-libs)	21s
build (ubuntu-latest, examples/arduino-external-libs)	1m 48s
build (ubuntu-latest, examples/arduino-internal-libs)	1m 49s
build (ubuntu-latest, examples/arduino-web-thing-led)	50s
build (ubuntu-latest, examples/zephyr-blink)	2m 0s
build (ubuntu-latest, examples/zephyr-drivers-lcd-hd44780)	1m 50s
build (ubuntu-latest, examples/zephyr-subsys-logger)	2m 8s
build (windows-latest, examples/arduino-blink)	4m 20s
build (windows-latest, examples/arduino-briki-internal-libs)	1m 24s
build (windows-latest, examples/arduino-external-libs)	3m 51s
build (windows-latest, examples/arduino-internal-libs)	3m 54s
build (windows-latest, examples/arduino-web-thing-led)	1m 42s
build (windows-latest, examples/zephyr-blink)	5m 57s
build (windows-latest, examples/zephyr-drivers-lcd-hd44780)	4m 16s
build (windows-latest, examples/zephyr-subsys-logger)	4m 47s
build (macos-latest, examples/arduino-blink)	2m 58s
build (macos-latest, examples/arduino-briki-internal-libs)	36s
build (macos-latest, examples/arduino-external-libs)	2m 35s
build (macos-latest, examples/arduino-internal-libs)	2m 43s
build (macos-latest, examples/arduino-web-thing-led)	1m 15s
build (macos-latest, examples/zephyr-blink)	3m 40s
build (macos-latest, examples/zephyr-drivers-lcd-hd44780)	3m 33s
build (macos-latest, examples/zephyr-subsys-logger)	3m 7s
	1h 3m 31s

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