Revert the homunculi and shadow sprites to original

Imported from legacy Flarum.
Original author: Vorpal (Flarum #234)

Now that monster sprites are reverted by patch #115, the homunculi and (floor) shadow sprites just don’t fit. Some homuns also have visible issues, like this Dieter:

P.S. You might also want to prohibit modifications of the shadow sprite as well.

Imported from legacy Flarum.
Original author: Muh (Flarum #1)

Sure thing, that was just an oversight