Plane: add missing AccZ bit from GCS_PID_MASK doc #34481

Job	Run time
build (chibios, Durandal)	17m 18s
build (chibios, MatekF405)	14m 42s
build (chibios, KakuteF7)	14m 5s
build (chibios, MatekH743-bdshot)	16m 55s
build (chibios, Pixhawk1-1M)	15m 38s
build (chibios, MatekF405-CAN)	1m 45s
build (chibios, DrotekP3Pro)	1m 46s
build (chibios, Hitec-Airspeed)	3m 7s
build (chibios, f103-GPS)	3m 4s
build (disco, armhf)	13m 45s
	1h 42m 5s

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