test: Fix the passing of arguments (#69)

This is needed to work with Ruby 3.0 or later.

```
  On subject Groonga::Client,
  unexpected method invocation:
    open(host: "127.0.0.1", port: 2929, protocol: :http, read_timeout: 60)
  expected invocations:
  - open({:host=>"127.0.0.1", :port=>2929, :protocol=>:http, :read_timeout=>60})
```

test/test-replayer.rb

@@ -51,7 +51,7 @@ def mock_client_open(expected_options)
           :read_timeout => 60,
         }
         expected_open_options = default_options.merge(expected_options)
-        mock(Groonga::Client).open(expected_open_options).yields(client) do
+        mock(Groonga::Client).open(**expected_open_options).yields(client) do
           client
         end
       end