Explicitly ignore the return value of cowboy_http_req:reply in error_response.

src/cowboy_http_protocol.erl

@@ -184,7 +184,7 @@ ensure_response(#http_req{resp_state=waiting}, State) ->
 -spec error_response(Code::http_status(), State::#state{}) -> ok.
 error_response(Code, #state{socket=Socket,
 		transport=Transport, connection=Connection}) ->
-	cowboy_http_req:reply(Code, [], [], #http_req{
+	_ = cowboy_http_req:reply(Code, [], [], #http_req{
 		socket=Socket, transport=Transport,
 		connection=Connection, resp_state=waiting}),
 	ok.