Add version information for 1.20.6 (#1310)

https://www.minecraft.net/en-us/article/minecraft-java-edition-1-20-6

api/src/main/java/com/velocitypowered/api/network/ProtocolVersion.java

@@ -86,7 +86,7 @@ public enum ProtocolVersion implements Ordered<ProtocolVersion> {
   MINECRAFT_1_20(763, "1.20", "1.20.1"),
   MINECRAFT_1_20_2(764, "1.20.2"),
   MINECRAFT_1_20_3(765, "1.20.3", "1.20.4"),
-  MINECRAFT_1_20_5(766, "1.20.5");
+  MINECRAFT_1_20_5(766, "1.20.5", "1.20.6");
 
   private static final int SNAPSHOT_BIT = 30;