Fix typo

Author: Ace Nassri

video/system-test/analyze.test.js

@@ -24,7 +24,7 @@ const cmd = `node analyze.js`;
 // analyze_faces
 test(`should analyze faces`, async (t) => {
   const output = await runAsync(`${cmd} faces gs://nodejs-docs-samples/video/google_gmail.mp4`);
-  t.regex(output, 'Thumbnail size: \d+');
+  t.regex(output, /Thumbnail size: \d+/);
 });
 
 // analyze_labels