pico-imx7d: remove unused 'script' variable

Since the pico-pi uses the distroboot,
this commit remove the 'script' variable (cf boot_scripts).
Signed-off-by: NPierre-Jean Texier <pjtexier@koncepto.io>
Reviewed-by: NFabio Estevam <festevam@gmail.com>

include/configs/pico-imx7d.h

@@ -79,7 +79,6 @@
 #define CONFIG_SYS_MMC_IMG_LOAD_PART	1
 
 #define CONFIG_EXTRA_ENV_SETTINGS \
-	"script=boot.scr\0" \
 	"image=zImage\0" \
 	"splashpos=m,m\0" \
 	"console=ttymxc4\0" \