testing/refind: add bash and lsblk to runtime depends (for refind-install)

Required for refind-install to work; it throws a "file or directory not found" error otherwise. (lsblk is used for some detection logic, there's also another package which it only needs for searching for unmounted partitions and shows an informational message if it's not installed so I think we can leave it out.)

It's not a dependency for the actual bootloader itself, but neither is efibootmgr (which was in depends already).