test/test_socket.rb spuriously fails

There was a spurious CI failure before, at line 295 in test/test_socket.rb, test test_can_create_socket_server_and_blocking_select_blocks_on_it()

I think the select timeout needs to be lengthened, so the Timeout::timeout is more likely to trigger before select wakes up (sleep granularity and context switching may cause them to occur not in the order desired).