Fix renaming of corpus_bleu args
Last `sacrebleu` release (v2.0.0) has renamed `sacrebleu.corpus_bleu` args from `(sys_stream, ref_streams)` to `(hipotheses, references)`: https://github.com/mjpost/sacrebleu/pull/152/files#diff-2553a315bb1f7e68c9c1b00d56eaeb74f5205aeb3a189bc3e527b122c6078795L17-R15

This PR passes the args without parameter names, so that it is valid for all versions of `sacrebleu`.

This is a partial hotfix of #2781.

Close #2781.