Pretty-printer does disambiguation of 'do' that is no longer necessary

[brson]

See pretty/block-arg-disambig, pretty/disamb-stmt-expr

[emberian]

Still relevant

[brson]

The issue is that do pretty prints as (do foo { }), with parens.

[catamorphism]

I believe this is no longer an issue; when I added expr_paren to the AST, I removed all cases where the pretty-printer inserts parens. Closing.