fedora: add dbus-broker to iot-simplified-installer dracut modules

With the sources update, the iot-simplified-installer in Fedora 40
started failing in the dracut stage with:

    dracut[I]: Module 'dbus-daemon' will not be installed, because command 'dbus-daemon' could not be found!
    dracut[E]: Module 'dbus' depends on 'dbus-daemon', which can't be installed
    dracut[E]: Module 'network-manager' depends on 'dbus', which can't be installed
    ...

This seems to be related to this change (which is included in dracut 060
in Fedora 40):
dracutdevs/dracut@3f8f115

The dbus dracut module has a dependency on either dbus-daemon or
dbus-broker.  In the past, simply installing dbus-broker was enough to
satisfy the dependency because the `find_binary` function would find the
dbus-broker binary.  The change to `check_module` requires the module to
be explicitly enabled, otherwise it falls back to dbus-daemon.

pkg/distro/fedora/images.go

@@ -785,6 +785,8 @@ func iotSimplifiedInstallerImage(workload workload.Workload,
 		}
 	}
 
+	img.AdditionalDracutModules = append(img.AdditionalDracutModules, "dbus-broker")
+
 	d := t.arch.distro
 	img.Product = d.product
 	img.Variant = "IoT"