fix build fail on tls1_3_md_max_size

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index fb61166..ceaf058 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -307,9 +307,7 @@
       + ( MBEDTLS_SSL_CID_OUT_LEN_MAX ) )
 #endif
 
-#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
 #define MBEDTLS_TLS1_3_MD_MAX_SIZE         MBEDTLS_MD_MAX_SIZE
-#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
 
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
 /**