boards: shields: nxp_m2_wifi_bt remove oob-gpios

Remove oob-gpios property from nxp_m2_1xk_wifi_bt.overlay. There is no
binding for this property at bindings\wifi\nxp,wifi.yaml. Therefore,
builds using this shield will fail.

Signed-off-by: Jacob Wienecke <jacob.wienecke@nxp.com>