boards: imx93_evk_mimx9352_m33_ddr.yaml: remove 'flash: 0'

It was preventing this variant (imx93_evk/mimx9352/m33/ddr) to show up
in the boards documentation. Other similar boards with similar DDR variants
(e.g. imx95_evk/mimx9596/m7/ddr) don't include this 'flash: 0' line.

Signed-off-by: Diego Herranz <diegoherranz@diegoherranz.com>

Author: diegoherranz

boards/nxp/imx93_evk/imx93_evk_mimx9352_m33_ddr.yaml

@@ -9,7 +9,6 @@ toolchain:
   - zephyr
   - cross-compile
 ram: 4096
-flash: 0
 supported:
   - gpio
   - uart