arrow

MINOR: [Release] Support GitHub token in download_rc_binaries.py (#44666)

### Rationale for this change

See apache/arrow-adbc#2307. This script is getting rate-limited on GitHub Actions.

### What changes are included in this PR?

Pick up GH_TOKEN if it exists.

### Are these changes tested?

N/A

### Are there any user-facing changes?

N/A

Authored-by: David Li <li.davidm96@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>