I thought that I saw a solder blob on the A0 address selection jumper. Change the I2C address in the sketch to 0x41.
Make it look like this:
// called this way, it uses the default address 0x40
//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
// you can also call it with a different address you want
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x41);