Remove 12 characters limitation when creating a new account

[lucca65]

Story

I as a regular user
Want to create simpler and easier to grasp account names
To enjoy having a less complicated account name to choose from when registering

Use cases

Given a new user
When we are validating the User module during sign Up
Then we don't require it to have 12 characters

Description

We don't really need to limit it anymore, we can simply not validate and allow shorter names