docs: fix example in Recipe: Capture Unconverted Fields

[ytjmt]

I've fixed the example in Recipe: Capture Unconverted Fields. https://ruby.github.io/csv/doc/csv/recipes/parsing_rdoc.html#label-Recipe-3A+Capture+Unconverted+Fields

parsed is wrong: header row is missing and the values should be integers.

$ ruby -v
ruby 3.2.1 (2023-02-08 revision 31819e82c8) [x86_64-darwin21]

$ cat unconverted_fields.rb
require "csv"

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
parsed = CSV.parse(source, converters: :integer, unconverted_fields: true)
p parsed
parsed.each {|row| p row.unconverted_fields }

$ ruby unconverted_fields.rb
[["Name", "Value"], ["foo", 0], ["bar", 1], ["baz", 2]]
["Name", "Value"]
["foo", "0"]
["bar", "1"]
["baz", "2"]

[kou]

Good catch!