Remove used of deprecated function in mbedtls

Upgrading to v3.6.2 introduced the deprecation of a function. This has
been migrated to the function that will be supported moving forward.

Change-Id: Ia7b06dcf066085bdfa027abe04fb0635257bfb18
Reviewed-on: https://pigweed-review.googlesource.com/c/open-dice/+/258352
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Darren Krahn <dkrahn@google.com>
Reviewed-by: Darren Krahn <dkrahn@google.com>
diff --git a/third_party/mbedtls/custom_config.h b/third_party/mbedtls/custom_config.h
index bcb1ead..765eef9 100644
--- a/third_party/mbedtls/custom_config.h
+++ b/third_party/mbedtls/custom_config.h
@@ -16,6 +16,7 @@
 #define THIRD_PARTY_MBEDTLS_CUSTOM_CONFIG_H_
 
 /* mbed TLS feature support */
+#define MBEDTLS_DEPRECATED_REMOVED
 #define MBEDTLS_ECDSA_DETERMINISTIC
 #define MBEDTLS_ECP_DP_SECP256R1_ENABLED
 #define MBEDTLS_SHA512_NO_SHA384