fix compiler warning about deprecated symbol

[skybrian]

Here is the warning: "'B10000000' is deprecated: use 0b10000000 instead"

I don't believe this change should have any effect at runtime.

[caternuson]

Looks OK. What was the original board being built for that created the warn?

[skybrian]

I'm using the unofficial Arduino port for the Raspberry Pi Pico:
https://github.com/earlephilhower/arduino-pico

And the microcontroller board is this one:
https://www.adafruit.com/product/5723

[caternuson]

Thanks, recreated:

/home/user/Arduino/libraries/Adafruit_MPR121/Adafruit_MPR121.cpp:109:7: warning: 'B10000000' is deprecated: use 0b10000000 instead [-Wdeprecated-declarations]
  109 |       B10000000 + 12; // 5 bits for baseline tracking & proximity disabled + X
      |       ^~~~~~~~~

This fix and change is actually part of PR #43, which is ready to be merged but was waiting for the user that opened the original issue to test. I think we'll just merge that one and it'll take care of this.