examples/quota-watermark: remove example

examples/quota-watermark: remove example

Original DPDK rings code had explicit support for a
single watermark per-ring, but more recent releases of
DPDK had a more general mechanism where each enqueue
or dequeue call could return the remaining elements/free-slots
in the ring.
Therefore, this example is not as relevant as before and can be removed.

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>