Update copyright for doc update test

AtsushiSakai · web-flow · commit 331f0877f6ad · 2023-12-03T21:56:04.000+09:00
diff --git a/docs/conf.py b/docs/conf.py
@@ -19,7 +19,7 @@
 # -- Project information -----------------------------------------------------
 
 project = 'PythonRobotics'
-copyright = '2018-2021, Atsushi Sakai'
+copyright = '2018-2023, Atsushi Sakai'
 author = 'Atsushi Sakai'
 
 # The short X.Y version
