Remove enableTLS13Handshake.

There is no longer need for the Go code to implement 'fake TLS 1.3'. We
now implement real incomplete TLS 1.3.

Change-Id: I8577100ef8c7c83ca540f37dadd451263f9f37e6
Reviewed-on: https://boringssl-review.googlesource.com/8823
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/ssl/test/runner/conn.go b/ssl/test/runner/conn.go
index c9bf2b1..a9e9231 100644
--- a/ssl/test/runner/conn.go
+++ b/ssl/test/runner/conn.go
@@ -1143,12 +1143,12 @@
 		m = new(encryptedExtensionsMsg)
 	case typeCertificate:
 		m = &certificateMsg{
-			hasRequestContext: c.vers >= VersionTLS13 && enableTLS13Handshake,
+			hasRequestContext: c.vers >= VersionTLS13,
 		}
 	case typeCertificateRequest:
 		m = &certificateRequestMsg{
 			hasSignatureAlgorithm: c.vers >= VersionTLS12,
-			hasRequestContext:     c.vers >= VersionTLS13 && enableTLS13Handshake,
+			hasRequestContext:     c.vers >= VersionTLS13,
 		}
 	case typeCertificateStatus:
 		m = new(certificateStatusMsg)
@@ -1536,7 +1536,7 @@
 		return nil, errors.New("tls: handshake has not yet been performed")
 	}
 
-	if enableTLS13Handshake && c.vers >= VersionTLS13 {
+	if c.vers >= VersionTLS13 {
 		// TODO(davidben): What should we do with useContext? See
 		// https://github.com/tlswg/tls13-spec/issues/546
 		return hkdfExpandLabel(c.cipherSuite.hash(), c.exporterSecret, label, context, length), nil