Replace downloadAndUnzipVSCode('insiders') with 'stable' in test runner (#981)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: nturinski <5290572+nturinski@users.noreply.github.com>

Author: Copilot

test/runTest.ts

@@ -9,7 +9,7 @@ import * as path from 'path';
 
 async function main(): Promise<void> {
     try {
-        const vscodeExecutablePath = await downloadAndUnzipVSCode('insiders');
+        const vscodeExecutablePath = await downloadAndUnzipVSCode('stable');
         const [cli, ...args] = resolveCliArgsFromVSCodeExecutablePath(vscodeExecutablePath);
 
         cp.spawnSync(