Fix set_brightness() comments

0 is not off, it's 1/16 brightness

Author: sfe-SparkFro

examples/qwiic_alphanumeric_ex04_set_brightness.py

@@ -59,8 +59,8 @@ def run_example():
     while True:
         for i in range(0, 16):
             # The input to set_brightness() is a duty cycle over 16
-            # So, the acceptable inputs to this function are ints between 0 (display off)
-            # and 15 (full brightness)
+            # So, the acceptable inputs to this function are ints between 0
+            # (1/16 brightness) and 15 (full brightness)
             my_display.set_brightness(i)
             time.sleep(1)
             my_display.print("Milk")

qwiic_alphanumeric.py

@@ -476,7 +476,7 @@ def set_brightness(self, duty):
             This function sets the brightness of all displays on the bus.
             Duty cycle over 16.
 
-            :param duty: Valid between 0 (display off) and 15 (full brightness)
+            :param duty: Valid between 0 (1/16 brightnss) and 15 (full brightness)
             :return: True if brightness is successfully updated, false otherwise.
             :rtype: bool
         """