Update draft-irtf-cfrg-curves-11 references to RFC 7748.

Change-Id: I6148df93a1748754ee6be9e2b98cc8afd38746cb
Reviewed-on: https://boringssl-review.googlesource.com/6960
Reviewed-by: Adam Langley <alangley@gmail.com>
diff --git a/ssl/test/runner/key_agreement.go b/ssl/test/runner/key_agreement.go
index 4f399d9..9ecd2e5 100644
--- a/ssl/test/runner/key_agreement.go
+++ b/ssl/test/runner/key_agreement.go
@@ -312,8 +312,7 @@
 	copy(peerKeyCopy[:], peerKey)
 	curve25519.ScalarMult(&out, &e.privateKey, &peerKeyCopy)
 
-	// Per draft-irtf-cfrg-curves-11, reject the all-zero value in constant
-	// time.
+	// Per RFC 7748, reject the all-zero value in constant time.
 	var zeros [32]byte
 	if subtle.ConstantTimeCompare(zeros[:], out[:]) == 1 {
 		return nil, errors.New("tls: X25519 value with wrong order")