west.yml: MCUboot synchronization from upstream

Update Zephyr fork of MCUboot to revision:
  e9131ee8b8ab9306d8f6ad410fd1e3d8a820ce10

Brings following Zephyr relevant fixes:
 - e9131ee8 zephyr: kconfig: Make saving encrypt TLVs depending
   on encryption
 - 4c7942e5 zephyr: Add estimated image footer size to cache in
   sysbuild
 - 26d6423b boot: zephyr: esp32: zephyr port

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