Change default max-nick-length to 16

[Phosphorshy]

Feature description

Change max nick length to 16 (from 15) to align with Minecraft's native username limit

How the feature is useful

Since Minecraft's native username limit is 16 the default max nickname should match that, the default of 15 can cause occasional issues for this reason as well.

Specifically if a server is set to only allow color changes on a nickname, a user with a 16 character name will not be able to change their username color on default max-nick-length configuration due to the nickname being "too long". (regardless of ignore-colors-in-max-nick-length setting)

While a server admin can easily fix this issue I don't see why the default couldn't already prevent it.