Remove GCC 12 warning in Vendor example

[earlephilhower]

Fixes GCC 12 warning for unused parameter found in CI here:

/home/runner/work/arduino-pico/arduino-pico/libraries/Adafruit_TinyUSB_Arduino/examples/Vendor/i2c_tiny_usb_adapter/Adafruit_USBD_I2C.cpp:67:60: error: unused parameter 'itfnum_deprecated' [-Werror=unused-parameter]
   67 | uint16_t Adafruit_USBD_I2C::getInterfaceDescriptor(uint8_t itfnum_deprecated, uint8_t* buf, uint16_t bufsize) {
      |                                                    ~~~~~~~~^~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors

[hathach]

Thank you