Remove `enabledApiProposals: ["testCoverage"]`?

[The-Compiler]

In #10, enabledApiProposals : ["testCoverage"] was added to package.json, as well as some other related changes there.

@starlord-daniel, is this really needed? From what I understand, this would enable a proposed test coverage API, but I don't really see this PR using it anywhere? From what I understand, all it uses is the Testing API, no?

[The-Compiler]

Those changes seem to break the build on main in ways I really don't understand... so I reverted them for now. Please let me know if that breaks anything for you, otherwise I suppose we can close this.

[The-Compiler]

Closing this for now.