Disabling i2c internal pull up resistors
From the datasheet:


  Note that the internal pull-ups in the AVR pads can be enabled by setting the PORT bits corresponding to the SCL and SDA pins, as explained in the I/O Port section.


To disable the internal pull-ups:

digitalWrite(A4, LOW);
digitalWrite(A5, LOW);


or

digitalWrite(2, LOW);
digitalWrite(3, LOW);