Compilation warning: `unused parameter 'size'`

Compilation of the core produces warnings for the unused `size` parameter of the `delete` operator:

```
/home/me/.arduino15/packages/arduino/hardware/avr/1.8.7/cores/arduino/new.cpp: In function 'void operator delete(void*, std::size_t)':
/home/me/.arduino15/packages/arduino/hardware/avr/1.8.7/cores/arduino/new.cpp:95:45: warning: unused parameter 'size' [-Wunused-parameter]
void operator delete(void* ptr, std::size_t size) noexcept {
^~~~
/home/me/.arduino15/packages/arduino/hardware/avr/1.8.7/cores/arduino/new.cpp: In function 'void operator delete [](void*, std::size_t)':
/home/me/.arduino15/packages/arduino/hardware/avr/1.8.7/cores/arduino/new.cpp:98:48: warning: unused parameter 'size' [-Wunused-parameter]
void operator delete[](void * ptr, std::size_t size) noexcept {
```

Please mark those parameters with `[[gnu::unused]]` or `__attribute__((unused))`.

https://github.com/arduino/ArduinoCore-avr/blob/d5d1355b95fd57bbcd30b86db5dc0003440eee8d/cores/arduino/new.cpp#L95-L97

### Additional context

#### Related

- https://github.com/arduino/ArduinoCore-avr/pull/487
- https://github.com/arduino/ArduinoCore-avr/issues/508
- https://github.com/arduino/ArduinoCore-avr/pull/631

Open cores/arduino/new.cpp around lines 95-98 and inspect the two sized delete operators that trigger the unused-parameter warnings. Apply the requested unused-parameter marking and compile the Arduino AVR core with warnings enabled; done means those warnings no longer appear.

Written by the indexing model from the issue text.