Bump ENV_VERSION for _CurrentDocument (#13246)

Co-authored-by: Adam Turner <[email protected]>

Author: shimizukawa

sphinx/environment/__init__.py

@@ -71,7 +71,7 @@
 
 # This is increased every time an environment attribute is added
 # or changed to properly invalidate pickle files.
-ENV_VERSION = 64
+ENV_VERSION = 65
 
 # config status
 CONFIG_UNSET = -1