Fix flaky test and add screenshots

ts/test-node/license_comments_test.ts

@@ -14,9 +14,6 @@ import {
 
 describe('license comments', () => {
   it('includes a license comment at the top of every relevant file', async function test() {
-    // This usually executes quickly but can be slow in some cases, such as Windows CI.
-    this.timeout(10000);
-
     await forEachRelevantFile(async file => {
       let firstLine: string;
       let secondLine: string;