manifest: update zephyr

This commit brings in zephyr containing the fix against crashes
of nrf5340 net core when wfi instruction was followed by access
to the memory.

Signed-off-by: Andrzej Kuros <andrzej.kuros@nordicsemi.no>

west.yml

@@ -59,7 +59,7 @@ manifest:
  # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/guides/modules.html
  - name: zephyr
  repo-path: sdk-zephyr
- revision: 75f67930b8d5616b5c0745de03b14a45fec897ac
+ revision: bb6a7db2c510c743374e9a8340ac065e6ae996c8
  import:
  # In addition to the zephyr repository itself, NCS also
  # imports the contents of zephyr/west.yml at the above