Restore previous formatting to generated parser code

In 03a316e8dad2a33783760316809a9e3f719ac3d6, the following change was
made that removed a space after `->`:

```
-        ")(I,D) end, fun(Node, Idx) -> ",Transform," end)."]
+        ")(I,D) end, fun(", TransformArgs, ") ->",Transform," end)."]
```

The previous behavior is more idiomatic for human readers. Restoring
the previous behavior makes it easier to review diffs of generated
parsers when verifying changes.