Updates MySQL version references from 8.0.39 to 8.0.42 in GitHub Actions workflow test matrices to match current Aurora version as of #42120. --------- Co-authored-by: anthropic-code-agent[bot] <242468646+Claude@users.noreply.github.com> Co-authored-by: iansltx <472804+iansltx@users.noreply.github.com> Co-authored-by: Ian Littman <iansltx@gmail.com>