tls13: srv: improve DEBUG_MSG in case of TLS 1.2 disabled

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index eb0b528..52d2db6 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -1923,7 +1923,7 @@
         /* Check if server supports TLS 1.2 */
         if (!mbedtls_ssl_conf_is_tls12_enabled(ssl->conf)) {
             MBEDTLS_SSL_DEBUG_MSG(
-                1, ("Unsupported version of TLS 1.2 was received"));
+                1, ("TLS 1.2 not supported."));
             MBEDTLS_SSL_PEND_FATAL_ALERT(
                 MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
                 MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER);