west.yml: MCUboot synchronization from upstream

Update Zephyr fork of MCUboot to revision:
  aa4fa2b6e17361dd3ce16a60883059778fd147a9

Brings following Zephyr relevant fixes:

  - 557f84be bootutil: Move primary/secondary slot definition to
    bootutil_public
  - 82bd4a76 boot: bootutil: Fix pure image validation check with
    offset swap
  - fe8f9fc0 bootutil: Fixed security counter overflow detected to
    late
  - 10a3cffa boot: zephyr: boards: nrf54h20dk cpuapp add chosen
    code part
  - 86678000 zephyr: use REQUIRED in dt_nodelabel calls to fail
    early and with meaningful message
  - e0b84a0c zephyr: Fix FLASH_DEVICE_ID for nRF54H20 platform
  - 504847e3 bootutil: Fix PureEdDSA when flash base is not 0x0
  - aa229135 bootutil: Fix bootutil_aes_ctr_drop memset usage
  - 713b98b6 boot/boot_serial: build-time skip of the erasing of
    img status page

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