modules: mcuboot: kconfig: Remove wrong nRF53 multi image dependency

Removes a dependency on the nRF53 multi image update Kconfig that
required the secondary slots to be located in external flash, since
this has never been a requirement for sysbuild only for deprecated
child/parent image

Signed-off-by: Jamie McCrae <[email protected]>

Author: nordicjm

modules/mcuboot/boot/zephyr/Kconfig

@@ -133,7 +133,6 @@ config NRF53_MULTI_IMAGE_UPDATE
 	depends on FLASH_SIMULATOR
 	depends on FLASH_SIMULATOR_DOUBLE_WRITES
 	depends on !FLASH_SIMULATOR_STATS
-	depends on PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY
 	depends on BOOT_UPGRADE_ONLY || USE_NRF53_MULTI_IMAGE_WITHOUT_UPGRADE_ONLY
 	depends on $(dt_compat_enabled,$(DT_COMPAT_SIM_FLASH))
 	select NRF53_MCUBOOT_PRIMARY_1_RAM_FLASH