test/gopls/vulncheck: increase 'populate webview' test timeout

Change-Id: Iac9b6a434206324fbb71a9111d584a22bf5ffcfe
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/407115
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
TryBot-Result: kokoro <[email protected]>
Reviewed-by: Suzy Mueller <[email protected]>

Author: hyangah

test/gopls/vulncheck.test.ts

@@ -29,7 +29,8 @@ suite('vulncheck result viewer tests', () => {
 		vscode.Disposable.from(...disposables).dispose();
 	});
 
-	test('populates webview', async () => {
+	test('populates webview', async function () {
+		this.timeout(5000);
 		const webviewPanel = _register(
 			vscode.window.createWebviewPanel(webviewId, 'title', { viewColumn: vscode.ViewColumn.One }, {})
 		);