Add Note About Re-Login After Username Change

[magge-faf]

Issue:

When someone is changing their nick, they have to relog into FAF client again to make use of the chat - otherwise, they are unable to connect to the chat. They do not see any error message that could indicate it.

Solution (kinda):

Add a text for better clarity to the change-page: https://www.faforever.com/account/changeUsername until the underlying issue gets resolved one day.

e.g.

After renaming, you have to relogin into FAF Client to make use of the chat.

(Or any other text you prefer. Not all will read it, but at least we can point to it, instead of explaining it in Discord every time when users can not use Aeolus)