Remove dead prototype.

Change-Id: I1d86c048eed6b616915bc4e3e9f2120098d15af7
Reviewed-on: https://boringssl-review.googlesource.com/5678
Reviewed-by: Adam Langley <agl@google.com>

ssl/internal.h

diff --git a/ssl/internal.h b/ssl/internal.h
index 3dca750..40ca00b 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -997,8 +997,6 @@
 int ssl3_send_next_proto(SSL *s);
 int ssl3_send_channel_id(SSL *s);
 
-int dtls1_client_hello(SSL *s);
-
 /* some server-only functions */
 int ssl3_get_initial_bytes(SSL *s);
 int ssl3_get_v2_client_hello(SSL *s);