kconfig: Remove version from boot banner

Removes the "version" part of the boot banner output as this is
already implied with the v prefix on the version number.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

Kconfig.nrf

@@ -30,7 +30,7 @@ menu "Nordic nRF Connect"
 
 # Override boot banner
 config BOOT_BANNER_STRING
-	default "Booting nRF Connect SDK version"
+	default "Booting nRF Connect SDK"
 
 # Override configuration from zephyr which sets this to 0x200 if MCUboot is
 # enabled (CONFIG_BOOTLOADER_MCUBOOT), since NCS use partition_manager to