manifest: update zephyr to contain nrf21540 tx-en timing fix

This PR brings Zephyr with updated default `tx-en-settle-time-us`
for the nrf21540 FEM to fix the spurious emission issue.

Signed-off-by: Andrzej Kuros <[email protected]>

Author: ankuns

west.yml

@@ -65,7 +65,7 @@ manifest:
     # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/guides/modules.html
     - name: zephyr
       repo-path: sdk-zephyr
-      revision: 59a8d2d1692d43086c0343e9ba87a800a2e93bc4
+      revision: 4575fc863ae46dc0f65593cb741660ddab1ba344
       import:
         # In addition to the zephyr repository itself, NCS also
         # imports the contents of zephyr/west.yml at the above