[Ruby] Table#initialize examples are out of date

https://www.rubydoc.info/gems/red-arrow/Arrow/Table
```ruby

count_field = Arrow::Field.new("count", :uint32)
count_array = Arrow::UInt32Array.new([0, 2, nil, 4])
count_column = Arrow::Column.new(count_field, count_array)
visible_field = Arrow::Field.new("visible", :boolean)
visible_array = Arrow::BooleanArray.new([true, nil, nil, false])
visible_column = Arrow::Column.new(visible_field, visible_array)
Arrow::Table.new(Arrow::Schema.new([count_field, visible_field]),
[count_column, visible_column])
```

```

NoMethodError (undefined method `schema' for #)
```

I would write tests but I presume that the interface has changed and the docs have been left behind. Please advise on how I could help out.

**Reporter**: [fonsan](https://issues.apache.org/jira/browse/ARROW-10587) / @Fonsan

_{**Note**: *This issue was originally created as [ARROW-10587](https://issues.apache.org/jira/browse/ARROW-10587). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start with the linked Ruby API documentation for Arrow::Table and the migration documentation, then reproduce the reported NoMethodError from the example. Compare the example with the current Table#initialize interface; done means the documented example runs without the reported error and reflects the current API.

Written by the indexing model from the issue text.