Reduce AvatarRenderedSizeFactor to 3

Save a bit of bandwidth by only requesting 3-times the rendered avatar
size. Factor 4 is only really beneficial on a handful of mobile phones
and I don't think they are the primary device we design for.

Fixes: #17422
Fixes: #16287

models/avatars/avatar.go

@@ -22,7 +22,7 @@ import (
 const DefaultAvatarPixelSize = 28
 
 // AvatarRenderedSizeFactor is the factor by which the default size is increased for finer rendering
-const AvatarRenderedSizeFactor = 4
+const AvatarRenderedSizeFactor = 3
 
 // EmailHash represents a pre-generated hash map (mainly used by LibravatarURL, it queries email server's DNS records)
 type EmailHash struct {