Update references to the extended master secret draft.

It's now an RFC too.

Change-Id: I2aa7a862bf51ff01215455e87b16f259fc468490
Reviewed-on: https://boringssl-review.googlesource.com/7028
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/tls1.h

diff --git a/include/openssl/tls1.h b/include/openssl/tls1.h
index 92d2752..e0f1399 100644
--- a/include/openssl/tls1.h
+++ b/include/openssl/tls1.h
@@ -218,7 +218,7 @@
 /* ExtensionType value from RFC7685 */
 #define TLSEXT_TYPE_padding 21
 
-/* https://tools.ietf.org/html/draft-ietf-tls-session-hash-01 */
+/* ExtensionType value from RFC7627 */
 #define TLSEXT_TYPE_extended_master_secret 23
 
 /* ExtensionType value from RFC4507 */