Fixes the EXTREME_HILLS_EDGE biome not being included in org.bukkit.block.Biome. Fixes BUKKIT-5433
Without this change the biome EXTREME_HILLS_EDGE cannot be found in
the Biome class.  This is a problem because if a plugin developer wants to
get a list of all biomes that exist his list would be inaccurate.  This commit
addresses this by adding the missing biome.