Change avar shaman and ma'xeochicatl to cast Brittle instead of Shatter.

Shatter itself is seen as more of a griefing spell, and these two monsters often use it to that effect. Shroud no longer protects shillings and number items from Shatter, thus there is no mechanism available to protect against it. Ideally Shatter will be modified or replaced in the future but for now, these two monsters will cast Brittle instead.

This also provides slightly more challenge in fighting the monster as the player will need to pay attention to his weapon (or shroud it). Mana Bombing the monster is also a viable defense, as it will (usually) take all their mana and leave them unable to cast such a high mana spell.