docs/esp8266/quickref: Polish Pin.on()/off() examples.

docs/esp8266/quickref.rst

@@ -107,9 +107,9 @@ Use the :ref:`machine.Pin <machine.Pin>` class::
     from machine import Pin
 
     p0 = Pin(0, Pin.OUT)    # create output pin on GPIO0
-    p0.on()                 # turn on pin, set to high
-    p0.off()                # turn off pin, set to low
-    p0.value(1)             # set pin to high
+    p0.on()                 # set pin to "on" (high) level
+    p0.off()                # set pin to "off" (low) level
+    p0.value(1)             # set pin to on/high
 
     p2 = Pin(2, Pin.IN)     # create input pin on GPIO2
     print(p2.value())       # get value, 0 or 1