`webdev` integration test has begun failing with `pub` error

[elliette]

The webdev integration test has begun failing with the lastest Dart main: 3.5.0-edge.cf4a4a3c00a4e160b3c924cc3081582dd42b26f7

See workflow run: https://github.com/dart-lang/webdev/actions/runs/8558545248/job/23459807649?pr=2403

Looks like the pub failure message was added here: dart-lang/pub#4171