bperrybap:
That library GitHub - FabioCuomo/FabioCuomo-DS3231: A modified arduino library for DS3231 RTC
does appear to call Wire.begin() in the library begin() method which means you can leave out the Wire.begin() call in your sketch; however, don't expect much code reduction (it should save a few bytes) as the only thing you are saving is an additional call to Wire.begin() in your setup() code.
Thanks!