Use Parser::Source::Rewriter

[yujinakayama]

• https://github.com/whitequark/parser/pull/403
• https://github.com/whitequark/parser/blob/v2.5.1.2/lib/parser/source/tree_rewriter.rb
• https://github.com/whitequark/parser/blob/v2.5.1.2/lib/parser/source/rewriter.rb#L7-L20