Exclude MT_BOXSPARKLE from Mario blocks

I noticed that respawnable monitors aren't really usable in Mario blocks because of the sparkles they spawn. I looked at the code and see a long list of objects which should be excluded, and as I expected, that one was missing. So I went ahead and added it to the list.

I still think it might be better to ditch that list and just use a flag for it, so custom objects can be ignored if desired, but at least this fixes the issue with respawnable monitors.

Here's a small map that demonstrates the bug, which can be used to verify the fix.