Update fedora.rst

It looks like ``wmdocker`` does not have an update for Fedora 20:

```
~❯ pkgwat releases wmdocker
Starting new HTTPS connection (1): apps.fedoraproject.org
+---------------+----------------+-----------------+
| release       | stable_version | testing_version |
+---------------+----------------+-----------------+
| Rawhide       | 1.5-12.fc21    | None            |
| Fedora 20     | None           | None            |
| Fedora 19     | None           | None            |
| Fedora EPEL 7 | None           | None            |
| Fedora EPEL 6 | None           | None            |
| Fedora EPEL 5 | None           | None            |
+---------------+----------------+-----------------+
```

I'm not sure if the owner awjb is intending to create an F20 update or not, but either way -- these docs are incorrect as currently written.