Fix linting error.

micropython/modules_py/pimoroni.py

@@ -187,7 +187,7 @@ class PID:
 class Buzzer:
     def __init__(self, pin):
         self.pwm = PWM(Pin(pin))
-    
+
     def set_tone(self, freq, duty=0.5):
         if freq < 50.0:  # uh... https://github.com/micropython/micropython/blob/af64c2ddbd758ab6bac0fcca94c66d89046663be/ports/rp2/machine_pwm.c#L105-L119
             self.pwm.duty_u16(0)