solver: general spec overrides specific spec in dependencies

The below dependencies resolve in the following manner:
``` yaml
dependencies:
  - spec: ubuntu@18.04:22.04
    when: distro=ubuntu cuda@11.8.0
  - spec: gcc@6:11
    when: cuda@11
  - spec: gcc
```

``` bash
$ velocity spec cuda
    created recipe in 4.52s

  > cuda@11.8.0-86ac71a
     ^ubuntu@22.04-32b95db
     ^gcc@15.2.0-8bb3e35
        ^ubuntu@22.04-32b95db
```

This is a solver bug.