Use Insiders edition in test runner

Author: garrytrinder

.vscode-test.mjs

@@ -2,6 +2,7 @@ import {defineConfig} from '@vscode/test-cli';
 
 export default defineConfig({
   files: 'out/test/**/*.test.js',
+  version: 'insiders',
   mocha: {
     ui: 'tdd',
     timeout: 20000,