Fix incorrect use of braces on S-expressions.
Fix incorrect use of braces on S-expressions.

Due to accidentally typing `braced` instead of `parened`, the
S-expression (eg) `(+ (- 1 2) 3)` was being pretty-printed as
`{+ {- 1 2} 3}`.  This minor fix corrects that behaviour.

septract/starling-tool,septract/starling-tool