west.yml: MCUboot synchronization from upstream

Update Zephyr fork of MCUboot to revision:
  4e108f702b5322fb59344ae4976e3d73c973ef12

Brings following Zephyr relevant fixes:

  - 4e108f70 boot: zephyr: adjust sample.yaml to pass USB
    deprecation process
  - 29690581 boot: zephyr: boards: update name of nrf54h20dk
  - cb92ebeb boot: zephyr: boards: nrf52: Fix minimal config
  - 1d7fe64b boot: zephyr: boards: nrf54l15dk: Remove invalid
    Kconfigs
  - c033b71b boot: zephyr: Remove reference to old Kconfigs
  - 268968f8 zephyr: Add support for AES256
  - a5c48f3c imgtool: Allow for AES256 encryption
  - fc8477e5 boot: bootutil: image_validate: Add error on security
    counter fail
  - d5f84b49 zephyr: Add support for slot selection boot hook
  - 7c4ec9ab loader: Add boot hook for slot selection
  - 94d85f91 imgtool: Fix x25519 TLV HMAC tag
  - 32db7886 bootutil: Fix X25519 HMAC-SHA512
  - 2bc36d0f bootutil: Expose hardware security counter
  - b475adf7 zephyr: Add CONFIG_BOOT_BYPASS_KEY_MATCH
  - 6d943d68 bootutil: Support for MCUBOOT_BYPASS_KEY_MATCH
  - e2e372f2 boot: Add config for dongle bare variant
  - dce784a2 loader: Allow to specify slot number in version
  - 5ee96f5b zephyr: Enable building ECDSA PSA variant

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