remove setting additional props on transforms

[WillBeebe]

There were some comments in the method I removed

• // json schema has a bug where if "anyOf", "allOf" or "oneOf" are used, additionalProperties MUST be true
• https://github.com/massdriver-cloud/xo/issues/53

I thought additionalProperties could be false or an object. The other link points to this page, which doesn't talk about this at all, maybe it's been addressed in JSON Schema?

https://json-schema.org/understanding-json-schema/reference/combining.html#:~:text=biggest%20surprises