Update a sample code (#2387)

Kernel#inspect does not call #to_s now

To follow https://github.com/ruby/ruby/commit/fd7dc23d281f38a71fa7f9c32812cd468c4b1788

1 files changed, 1 insertions, 1 deletions

diff --git a/sample/list3.rb b/sample/list3.rb
index 1d9f04b710..110e405cf9 100644
--- a/sample/list3.rb
+++ b/sample/list3.rb
@@ -7,7 +7,7 @@ class Point
     self
   end
 
-  def to_s
+  def inspect
     sprintf("%d@%d", @x, @y)
   end
 end