boards: frdm_mcxw71: doc: fix sample command typo

Changed from `:west-args:` to `:gen-args:` for specifying
config file.

Signed-off-by: Dipak Shetty <[email protected]>

Author: dipakgmx

boards/nxp/frdm_mcxw71/doc/index.rst

@@ -144,13 +144,13 @@ Openthread applications
    :zephyr-app: samples/net/sockets/echo_server
    :board: frdm_mcxw71
    :goals: build
-   :west-args: -- -DEXTRA_CONF_FILE=overlay-ot.conf
+   :gen-args: -DEXTRA_CONF_FILE=overlay-ot.conf
 
 .. zephyr-app-commands::
    :zephyr-app: samples/net/sockets/echo_client
    :board: frdm_mcxw71
    :goals: build
-   :west-args: -- -DEXTRA_CONF_FILE=overlay-ot.conf
+   :gen-args: -DEXTRA_CONF_FILE=overlay-ot.conf
 
 Application Flashing
 ====================