How can I permanently disable this update notification?
Go to File > Preferences > Settings (or hit Ctrl-,)
Here two files will open. One is "Default Settings" and other is "User Settings".
Add a new parameter in "User Settings"
"update.channel": "none"
Then save the files, VS Code will ask you to restart, and then you won't receive the update message.
update.channel is deprecated, use update.mode instead
"update.mode": "none"