[extension_discovery] CI always fails
See https://github.com/dart-lang/tools/actions/runs/16545246733
It looks like this started failing ~4 months ago. The dev channel build started failing first, then the stable build followed after. The sdk versions are no longer in the workflow logs, but I think we can assume the test is failing due to an sdk change.
I'll disable the test for now until an owner has time to investigate.
cc @jonasfj @sigurdm
Bisected the failure to https://github.com/dart-lang/pub/pull/4549
Still not sure why this fails. Perhaps extension_discovery depends on file timestamps to update, and after that change we no longer update the timestamp if the package_config is unchanged.