[presubmit] Delete old .packages file from package status_file
[presubmit] Delete old .packages file from package status_file

It caused the presubmit to fail with null safety errors.

Change-Id: Ie28a77af0d3663abacdd8b6de0e7645e2b613163
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/156685
Auto-Submit: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Commit-Queue: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Commit-Queue: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk