Update comment for TLSEXT_TYPE_renegotiate.

Change-Id: I2b831cf04e15116b849dae714d77602da4cbad91
Reviewed-on: https://boringssl-review.googlesource.com/1064
Reviewed-by: Adam Langley <agl@google.com>

ssl/tls1.h

@@ -243,7 +243,7 @@ extern "C" {
 /* ExtensionType value from RFC4507 */
 #define TLSEXT_TYPE_session_ticket		35
 
-/* Temporary extension type */
+/* ExtensionType value from RFC5746 */
 #define TLSEXT_TYPE_renegotiate                 0xff01
 
 #ifndef OPENSSL_NO_NEXTPROTONEG