This removes the "Input" and "Output" part of the default label in the
simulation and repeat zone. The outline already makes it very obvious
which one is the input and which one the output. Simplifying the label
makes the zone look prettier. It might also simplify naming other zones
(like for-each zone) in the future, because the name is shorter.
Pull Request: https://projects.blender.org/blender/blender/pulls/117724
153caeff4d