MIFARE RC522 I2C Library
SPI is a multi-slave bus. Unless you've run out of free pins to use for CS, or you have slaves that don't play nice, you can connect your RFID module to the SPI bus as well. Also your sketch will most likely compile if you only correct the offending line to simply Wire.begin(). Your library uses the standard Wire library but assumes the target is an ESP8266, whose version of Wire has an extended begin() method. 

But this may all be no use since the MFRC522 you have (assuming it's the cheap blue module) is hardwired to use only the SPI interface. Unless you're ready to modify the PCB (cut traces, etc) as others have done.