[doc] Example of servo sweep is wrong

[jvalrog]

The code for that example is wrong. It lacks delays so the sweep is useless.

The example file is this: https://github.com/adafruit/Adafruit_CircuitPython_PCA9685/blob/master/examples/pca9685_servo.py

And it differs from this other one from the Motor library (it's actually the same example but this one has delays): https://github.com/adafruit/Adafruit_CircuitPython_Motor/blob/master/examples/motor_pca9685_servo_sweep.py

[ladyada]

hi please submit a PR for a version with delays then

[jposada202020]

Closed by #36