Partly reverted r59642. Because IO#close is idempotent since Ruby 2.3.

Reported by Eric Wong. Thank you.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59683 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/csv.rb

@@ -1288,7 +1288,7 @@ class CSV
       begin
         yield csv
       ensure
-        csv.closed? || csv.close
+        csv.close
       end
     else
       csv