Fix #4881 (#4884)

Thanks Mike for noticing: In pxx_arm.cpp, the pulse duration is set to either 48 or 32. This value gets put into the ARR register of the timer (via DMA). Counters count from 0 to the ARR value, then go back to 0. This will result in either 49 or 33 counts for the pulse width, thus making the pulses 0.5uS too long.

Tested only with external PXX

radio/src/pulses/pxx_arm.cpp

@@ -134,7 +134,7 @@ void pxxPutPcmTail(uint8_t port)
 #else
 void pxxPutPcmPart(uint8_t port, uint8_t value)
 {
-  pulse_duration_t duration = value ? 48 : 32;
+  pulse_duration_t duration = value ? 47 : 31;
   *modulePulsesData[port].pxx.ptr++ = duration;
   modulePulsesData[port].pxx.rest -= duration + 1;
 }