round af/rx-/txdelay to 3 decimal places #637

Job	Run time
build (Heltec_v3_room_server)	2m 44s
build (PicoW_repeater)	2m 47s
build (RAK_4631_repeater)	2m 16s
build (RAK_4631_companion_radio_ble)	2m 17s
build (RAK_4631_room_server)	2m 15s
build (wio-e5-mini_repeater)	1m 34s
build (Heltec_v3_companion_radio_ble)	2m 44s
build (Heltec_v3_repeater)	3m 2s
build (LilyGo_Tlora_C6_repeater_)	1m 56s
	21m 35s

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