docs/esp32: Update RMT quickref example to match latest code.

The start keyword was removed in 18e48a7

Signed-off-by: Damien George <damien@micropython.org>

docs/esp32/quickref.rst

@@ -509,7 +509,7 @@ The RMT is ESP32-specific and allows generation of accurate digital pulses with
     r = esp32.RMT(0, pin=Pin(18), clock_div=8)
     r   # RMT(channel=0, pin=18, source_freq=80000000, clock_div=8)
     # The channel resolution is 100ns (1/(source_freq/clock_div)).
-    r.write_pulses((1, 20, 2, 40), start=0) # Send 0 for 100ns, 1 for 2000ns, 0 for 200ns, 1 for 4000ns
+    r.write_pulses((1, 20, 2, 40), 0) # Send 0 for 100ns, 1 for 2000ns, 0 for 200ns, 1 for 4000ns
 
 OneWire driver
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