ast: Codeblocks should not have extra trailing newlines
Description
We had some difficulties after the codegen-AST rework. This MR solves all of them that I found.
Checklist
-
You have read, and followed the guidance in, the CONTRIBUTING guide -
The MR content has run through a pipeline, or at least has pipelines enabled. -
There are no licence concerns with this contribution (The README clearly states Subplot is GPL-3.0)