docs: Wrong spelling in 'writeUint16LE'

[liuzeyafzy]

There is a wrong spelling in 'writeUint16LE'. It makes me who is a newbie confused.
page: 'api/buffer.html'

b.writeUint16LE(0x90ab, 0);

The function should be 'writeUInt16LE'.

[fhemberger]

/cc @nodejs/documentation

[evanlucas]

This documentation is actually stored in https://github.com/nodejs/node/blob/master/doc/api/buffer.markdown. Would you be interested in opening a pull request to fix that? I went ahead and opened an issue at nodejs/node#3223