manifest: Use Mbed TLS 3.0 based on upstream

Use a new branch of Mbed TLS 3.0 based on the upstream history rather
than our local version with a different directory layout.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/west.yml b/west.yml
index df172ee..f3e509c 100644
--- a/west.yml
+++ b/west.yml
@@ -153,7 +153,7 @@
       revision: 8e303c264fc21c2116dc612658003a22e933124d
       path: modules/lib/lz4
     - name: mbedtls
-      revision: 8c358faaaa09492c4c0d91d4a74806180cb8abd0
+      revision: bf66e18046a96e83b6ef3bb4bec0ae81bdcefc68
       path: modules/crypto/mbedtls
       groups:
         - crypto