[BUG]: Support new usernames

[rabeehrz]

Bot Version

4.0.1

How are you hosting Modmail?

Other

Error Logs

https://i.imgur.com/qhrdIjC.png

Screenshots

With Discord introducing new usernames, the embed the bot generates for reply contains #0 as the default discriminator.

I think only the username should be displayed.

In the above image, It should be aer instead of aer#0

Additional Information

No response

[byayex]

Would recommend waiting for changes on this until the new usernames are 100% rolled out.