CI: Fix FreeBSD 13.4 STABLE build

In openzfs#16869 we added FreeBSD 13.4 STABLE, but forget the special
thing, that the virtio nic within FreeBSD 13.x is buggy.

This fix adds the needed rtl8139 nic to the VM.

Reviewed-by: George Melikov <[email protected]>
Reviewed-by:  Alexander Motin <[email protected]>
Signed-off-by: Tino Reichardt <[email protected]>
Closes openzfs#16885

Author: mcmilk

.github/workflows/scripts/qemu-2-start.sh

@@ -93,6 +93,7 @@ case "$OS" in
     OSv="freebsd13.0"
     URLzs="$FREEBSD/amd64-freebsd-13.4-STABLE.qcow2.zst"
     BASH="/usr/local/bin/bash"
+    NIC="rtl8139"
     ;;
   freebsd14-2s)
     OSNAME="FreeBSD 14.2-STABLE"