move zeroize master secrets

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 2e26384..f219586 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -1646,8 +1646,7 @@
  */
 static int ssl_tls13_handshake_wrapup( mbedtls_ssl_context *ssl )
 {
-    mbedtls_platform_zeroize( &ssl->handshake->tls13_master_secrets,
-                              sizeof(ssl->handshake->tls13_master_secrets));
+
     mbedtls_platform_zeroize( &ssl->handshake->tls13_hs_secrets,
                               sizeof(ssl->handshake->tls13_hs_secrets));