manifest: Bring Zephyr with KMU reserved area fix

Bring updated Zephyr which does not include the linker
script which reserves the KMU buffer for non-XIP builds.

Signed-off-by: Georgios Vasilakis <georgios.vasilakis@nordicsemi.no>

west.yml

@@ -66,7 +66,7 @@ manifest:
     # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/guides/modules.html
     - name: zephyr
       repo-path: sdk-zephyr
-      revision: 107f9f0cf5369c707282724f7484d708a99ed274
+      revision: b91aa4fec5484f6cd076c9333bb474a7f5c002c1
       import:
         # In addition to the zephyr repository itself, NCS also
         # imports the contents of zephyr/west.yml at the above