Reduce image size a bit
Reduce image size a bit

Switch to buster-slim and remove qemu from the installed packages.
Cuttlefish defaults to crosvm.  If you need QEMU, you can install the
package manually.

Signed-off-by: Iliyan Malchev <b9962a40c76f189681da2829a74a26cab77021ea@gmail.com>

google/android-cuttlefish,google/android-cuttlefish,google/android-cuttlefish,google/android-cuttlefish,google/android-cuttlefish,google/android-cuttlefish,google/android-cuttlefish