no-url-literals is untested

```bash
git grep -E no-url
doc/manual/source/release-notes/rl-2.4.md:* The new experimental feature `no-url-literals` disables URL
src/libutil/experimental-features.cc:        .name = "no-url-literals",
src/libutil/experimental-features.cc:            $ nix repl --extra-experimental-features 'no-url-literals'

```

- Found out in #13489 