disable check for updates: support just one static version;

--- a/src/Tools/VSCode/src/vscode_setup.scala	Sun Feb 27 20:00:23 2022 +0100
+++ b/src/Tools/VSCode/src/vscode_setup.scala	Mon Feb 28 12:41:48 2022 +0100
@@ -46,7 +46,8 @@
   "editor.fontSize": 18,
   "editor.lineNumbers": "off",
   "editor.renderIndentGuides": false,
-  "editor.rulers": [80, 100]
+  "editor.rulers": [80, 100],
+  "update.mode": "none"
 }
 """)
     }