Fixed typo

docs/10.4-test-utils.md

@@ -175,7 +175,7 @@ Then you can assert:
 result = renderer.getRenderOutput();
 expect(result.type).toBe('div');
 expect(result.props.children).toEqual([
-  <span className="heading">Title</span>
+  <span className="heading">Title</span>,
   <Subcomponent foo="bar" />
 ]);
 ```