format: ignore println newline in foreign format hints fixes rust-lang/rust#158216 `println!` adds a newline before the unused-arg diagnostic checks for printf-style formats. that made a trailing `%` look like `%` plus ` `, so rustc printed a weird unsupported conversion specifier note. imo the least risky fix is to leave normal format parsing alone and only strip that synthetic newline for the foreign-format hint scan. idk if there is much more to do here, the ui tests cover the reported case plus the older trailing-percent baselines. lgtm to me, ltm this keeps the behavior narrow.