Switch over any avatarURL() calls to displayAvatarURL()

[rasmusgerdin]

avatarURL() returns the user's profile picture if they have one
https://discord.js.org/#/docs/main/master/class/User?scrollTo=avatarURL

displayAvatarURL() returns the user's profile picture if they have one, and their default profile picture if they haven't added one yet
https://discord.js.org/#/docs/main/stable/class/User?scrollTo=displayAvatarURL

[mcumbers]

9d88ef0