chore!: mark the obsolete Player.Class with the error flag

Plugin authors that want to release new versions of their plugin will have to
decide whether they want to use OriginalClass or CurrentClass.

Hearthstone Deck Tracker/Hearthstone/Player.cs

@@ -851,7 +851,7 @@ public IEnumerable<SingleCardStats>? MulliganCardStats
 			}
 		}
 
-		[Obsolete("Use OriginalClass or CurrentClass instead")]
+		[Obsolete("Use OriginalClass or CurrentClass instead", true)]
 		public string? Class => OriginalClass;
 	}
 }