core: render Render Blocking insight as a warning

[Manohar2503]

Summary

Changes the Render Blocking insight to be displayed as a warning (amber) instead of an error (red).

What changed

• Override the failed Render Blocking insight to use scoreDisplayMode: numeric
• Set the score to 0.5 for failed insights so it renders as an amber warning
• Regenerated core/test/results/sample_v2.json

Testing

• Ran renderer tests
• Regenerated sample_v2.json
• Ran yarn type-check
• Ran yarn lint

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[Manohar2503]

Hi @paulirish, just following up on this PR. Whenever you have a chance, I'd really appreciate a review. If there are any changes or improvements you'd like me to make, I'm happy to update the PR. Thanks for your time.