shadow_bevel.py and sphere.py are unfinished and have been in the
"Unstable" only builds for years. This is probably not worth porting
them. Let's just delete them.
I have actually move these (as well clothify and whirlpinch removed
yesterday) to the gimp-data-extras repository so if anyone wants to
revive them, and port them to GIMP 3, they can start off from there.
2271b5bbdb