Jose: The external resistors shown are probably not necessary.
The default Wire library enables the internal pullup resistors of the Arduino.
In fact, an update on the website you referred to notes this.
The only potential issue is that the internal pullup resistors are larger than that you are currently using, so it is possible that if your cable length going to the RTC is too long that the capacitance of the cable will cause the signals to be corrupted.
You probably do not have long signal wires going to RTC.
Just remove the external resistors and give it a try.