fix(MultiCast): let CoA custom classes (Witchdoctor) get the totem bar

Both MultiCastBar.lua and Options/MultiCastBar.lua hard-coded a class-mask
gate of SHAMAN|HERO, which doesn't know about CoA custom classes. As a
result, Witchdoctor (and any other CoA class the engine produces a totem
bar for) never had Bartender's wrapper module register, leaving the totem
bar un-skinned / un-configurable.

Keep the original mask check as the fast path, but fall through and load
the module when MultiCastActionBarFrame already exists — the engine only
creates that frame for classes that actually use the totem bar, so it's a
reliable class-agnostic test.

Bartender4/Options/MultiCastBar.lua

@@ -7,7 +7,10 @@ if not HasMultiCastActionBar then return end
 
 local classMask = UnitClassMask("player")
 
-if not bit.contains(EnumUtil.CombineMasks(Enum.ClassMask.SHAMAN, Enum.ClassMask.HERO), classMask) then
+-- CoA: see MultiCastBar.lua — same gate, same fallback so the options
+-- panel is registered for custom classes (e.g. Witchdoctor) too.
+if not bit.contains(EnumUtil.CombineMasks(Enum.ClassMask.SHAMAN, Enum.ClassMask.HERO), classMask)
+   and not MultiCastActionBarFrame then
 	return
 end