Remove call to SSL_CTX_set_tls_channel_id_enabled in bssl_shim.

Channel ID is already enabled on the SSL. This dates to
49c7af1c42 which converted an instance of
tlsext_channel_id_enabled_new to it, but tlsext_channel_id_enabled_new
meant "if Channel ID is enabled, use the new one", not "enable Channel
ID".

Thanks to Eric Rescorla for catching this.

Change-Id: I2d5a82b930ffcbe5527a62a9aa5605ebb71a6b9f
Reviewed-on: https://boringssl-review.googlesource.com/13042
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

ssl/test/bssl_shim.cc

@@ -983,7 +983,6 @@ static bssl::UniquePtr<SSL_CTX> SetupCtx(const TestConfig *config) {
     SSL_CTX_set_alpn_select_cb(ssl_ctx.get(), AlpnSelectCallback, NULL);
   }
 
-  SSL_CTX_set_tls_channel_id_enabled(ssl_ctx.get(), 1);
   SSL_CTX_set_channel_id_cb(ssl_ctx.get(), ChannelIdCallback);
 
   SSL_CTX_set_current_time_cb(ssl_ctx.get(), CurrentTimeCallback);