dartdev: skip 'pub outdated' check in tests
dartdev: skip 'pub outdated' check in tests

Fixes https://github.com/dart-lang/sdk/issues/42049

We should enable, and test this feature in these tests, I think.
But for now I just need the tests to start passing. I haven't wrapped
my head around how mock-y / end-to-end-y migrate_test is.

Change-Id: I7a2e2034b2a1f42b71d78f4776ee8711071f01f7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/149200
Commit-Queue: Samuel Rawlins <5cf2cac5eec2ad6d0eb2b0f4ff6af9a590ce2bf6@google.com>
Reviewed-by: Mike Fairhurst <2002604e76601be549134505841fea93de80dc45@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