VS Code: reduce test flakiness

The 'file on disk changes' test is flaking on CI servers. Increase the
delay to give VS Code more time to register its FS watches, hopefully
fixing the flakiness.

Author: strager

plugin/vscode/test/vscode-tests.js

@@ -161,7 +161,7 @@ tests = {
     let helloEditor = await vscode.window.showTextDocument(helloDocument);
 
     // HACK(strager): Wait for VS Code to register its filesystem watchers.
-    await sleepAsync(100);
+    await sleepAsync(300);
 
     fs.writeFileSync(helloFilePath, "let x = 3;\nlet x = 4;\n");