Don't overwrite the codecov/project status to green

[wilzbach]

Now that we CodeCov properly find the base commit, it will only error if the patch reduces the coverage of a file, which shouldn't happen too often.

Follow-up to #7711

[dlang-bot]

Thanks for your pull request, @wilzbach!

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[wilzbach]

So I went through page 1 of the open PRs and those two PRs would have been flagged:

• Group scattered AST visitors into a visitors package #7639
• Have one source of truth for the language transitions #7648

So it doesn't work well for refactorings or work with CTFE, so maybe sticking with informational: true and just being a bit more careful when looking at the diff is the best?

[JinShil]

I'm torn on this. I want it to be a requirement, but that red X is going to be just an annoyance if I have to visit each PR to see if it is only the codecov that's failing. I have to make a binary choice, so I vote "No".

[WalterBright]

As noted, it is impractical to require this. There's no substitute for the reviewer checking the uncovered new lines, and requiring that the ones that could be covered be covered, but these are a judgement call.