fix comments issue

Co-authored-by: Ronald Cron <ronald.cron@arm.com>
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index d6450a5..acd536a 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -763,7 +763,7 @@
  * ssl_tls13_write_supported_versions_ext():
  *
  * struct {
- *      ProtocolVersion versions<2..254>;
+ *      ProtocolVersion selected_version;
  * } SupportedVersions;
  */
 static int ssl_tls13_write_supported_versions_ext( mbedtls_ssl_context *ssl,