update vscode extension settings

Since denoland/vscode_deno v3.34.0 (Feb 25, 2024), command 'Deno: Initialize
Workspace Configuration' now is an alias for 'Deno: Enable' which only sets

    "deno.enable": true

See denoland/vscode_deno@4851ae73 (feat: restore init workspace command as
alias, 2024-01-31)

runtime/getting_started/setup_your_environment.md

@@ -35,9 +35,7 @@ following configuration:
 
 ```json
 {
- "deno.enable": true,
- "deno.lint": true,
- "deno.unstable": true
+ "deno.enable": true
 }
 ```