Redo the codecov config as soon as tarpaulin is able to check the coverage on every line

[1c3t3a]

Currently tarpaulin has some issues detecting dangling or formatted lines, see #351. This lead to some issues in #44 where the diff target was hit. I reconfigured the CI to shut up, but we should change it back as soon as tarpaulin is stable. The old config looked like this:

coverage: 
    status:
      project:
        default:        
          target: auto
          threshold: 2%
          paths:
             - "src"
         branches:
           - main
         if_ci_failed: ignore
         informational: false
         only_pulls: false