While working on #19989, I noticed that `--value(…)` inside functional
`@utility` definitions is not required right now.
That means that the following CSS is valid:
```css
@utility foo-* {
color: red;
}
```
But this doesn't really makes sense, because this now accepts a value
and `foo-a`, `foo-b` and `foo-c` would generate the following CSS:
```css
.foo-a {
color: red;
}
.foo-b {
color: red;
}
.foo-c {
color: red;
}
```
The `a`, `b`, and `c` are not doing anything here apart from making your
CSS bigger. So this is very likely an actual bug that you forgot to use
`--value(…)`.
Additionally, if a `--value(…)` was used, but it didn't resolve
anything, then we already properly discared the candidate.
## Test plan
1. Add test to ensure `--value(…)` is required in functional `@utility`
definitions
2. Existing tests pass
0f6f7d480f