Update flag sizes after switch to twemoji assets

The old flags used a size of 150x100, while the new assets based on
twemoji use a size of 150x108. Update existing usages to match this new
aspect ratio better.

osu.Game/Users/ExtendedUserPanel.cs

@@ -53,7 +53,7 @@ namespace osu.Game.Users
 
         protected UpdateableFlag CreateFlag() => new UpdateableFlag(User.Country)
         {
-            Size = new Vector2(39, 26),
+            Size = new Vector2(36, 26),
             Action = Action,
         };