manifest: mcuboot update

This update contains the version update which was reverted plus
relevant bugfixes.
The revert take places here: #50120

Synch up to the mcu-tools/mcuboot SHA:
73d69e9b566daac1a91724aa1237bfc1b9d51fa3

- Switched zephyr port from using FLASH_AREA_ macros to FIXED_PARTITION_
macros
- Made flash_map_backend.h compatible with a C++ compiler
- Enabled watchdog feed by default
- Allowed to get the flash write alignment basing on the zephyr,flash
DT chosen node property

- fixed watchdog device typos
- serial recovery: fixed build failure if CONFIG_BOOT_SERIAL_DETECT_PIN
has undefined value

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>