docs(v3): usage of `loadFromSamples` is wrong

[CosminPerRam]

sf::SoundBuffer::loadFromSamples usage in the v3 audio example docs is wrong:

One must provide loadFromSamples with 5 arguments, the docs shows a call with 4 arguments, which does not compile due to 5th not having a default value.

Example error message upon removing the 5th argument: error C2660: 'sf::SoundBuffer::loadFromSamples': function does not take 4 arguments

Explanation of this argument should also be expected to be here.

Thanks for the wonderful work!