Correct comment for backlight button functionality

Author: awjlogan

micropython/examples/pico_enviro/enviro_all.py

@@ -189,7 +189,7 @@ def draw_hist(results_array):
 time.sleep(0.5)
 
 while True:
-    # turn off the backlight with A and turn it back on with B
+    # turn on the backlight with A and turn it back off with B
     # switch between sensor and equaliser mode with X and Y
     if button_a.is_pressed:
         display.set_backlight(BRIGHTNESS)