fix typo

micropython/modules/pico_explorer/README.md

@@ -145,7 +145,7 @@ from pimoroni import Buzzer
 Then create a `Buzzer` instance:
 
 ```python
-BUZZER = Buzzer(0)
+buzzer = Buzzer(0)
 ```
 
 You can then play audio tones like this - frequency should probably be a number between 1 and 5000 if you have human ears. 
@@ -176,8 +176,8 @@ You can also use these pins as outputs, if you wanted to connect up stuff like L
 import machine
 
 GPO = machine.Pin(0, machine.Pin.OUT)
-
 ```
+
 Note that if you're connecting external LEDs up to Explorer Base, GP0-7 have built in 100 Ohm resistors, so you don't need to include a resistor in your circuit to protect your LED from drawing too much current.
 
 There's lots more info about how to use `machine` in the [Raspberry Pi documentation](https://www.raspberrypi.org/documentation/rp2040/getting-started/#getting-started-with-micropython).
@@ -204,6 +204,7 @@ from pimoroni_i2c import PimoroniI2C
 
 i2c = PimoroniI2C(sda=(20), scl=(21))
 ```
+
 ## Pins
 
 Here's a list of the pins associated with the various features of Pico Explorer. You can also find a list of pins on the underneath of the board!