Buffer.allocUnsafeSlow() allowed version in document is incorrect, actually is v5.12.0

[flarestart]

• Version: v6.2.0+
• Platform: N/A
• Subsystem: buffer, document

Buffer.allocUnsafeSlow() was added in v5.12.0

Source Code:

https://github.com/nodejs/node/blob/v5.10.0/lib/buffer.js
https://github.com/nodejs/node/blob/v5.12.0/lib/buffer.js line 160

In Documents

https://nodejs.org/dist/v6.2.0/docs/api/buffer.html#buffer_class_method_buffer_allocunsafeslow_size
...
https://nodejs.org/api/buffer.html#buffer_class_method_buffer_allocunsafeslow_size

[joyeecheung]

Yes, it was added in 5.12.0: 6a94383

I have labeled this as a good first contribution. Whoever wants to pick this one up can fix this by modifying the YAML section in doc/api/buffer.md