Fix the TwoWire destructor to use the array delete operator

[dewhisna]

The TwoWire::~TwoWire() destructor should use delete[] and not delete to correspond with the new uint8_t[bufferLength] in the constructor. It was mostly working by accident since the TwoWire objects are generally created globally and never destroyed. But depending on the library usage, having this wrong either causes the wrong operator to get called or link errors for a missing operator delete(void *, size_t) to be generated.