Allow depot_tools to update in tools/manage_deps.dart
Allow depot_tools to update in tools/manage_deps.dart

This became a problem with: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3556588 .

Change-Id: I00d16291112d63dff190a5553805f6185ea470b9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/239316
Reviewed-by: Jonas Jensen <c9327fa216ae2ef84df7c55b809d4ba270141b48@google.com>
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>
Commit-Queue: Sigurd Meldgaard <3f12f2c0f1efe4fd67753fcd55cd7bc21e5b85cf@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