Fix max_line_len not working for JSON files

As `maybe_newline()` is only called when `might_need_semicolon` is `true`, the `max_line_len` option has no effect for files without (or with very few) semicolons (like JSON files). A simple for this problem is to use `maybe_newline()` instead of `noop` as the `newline()` function in non-beautify mode.