`integration_test` failing on Dart SDK main due to recent pub changes

[elliette]

Some of the webdev integration_test cases are failing on the main branch of the Dart SDK, most likely due to dart-lang/pub#3844

These test cases seem to actually be testing pub validation, and string matching against the validation messages generated by pub. I don't think this is useful for us to test. We probably want to change the integration_test to actually test the validation that we control.

[bkonyi]

Is this still relevant @elliette?