fix shallowRenderer.getRenderOutput() return type in docs

docs/10.4-test-utils.md

@@ -217,7 +217,7 @@ shallowRenderer.render(
 Similar to `ReactDOM.render`.
 
 ```javascript
-ReactComponent shallowRenderer.getRenderOutput()
+ReactElement shallowRenderer.getRenderOutput()
 ```
 
 After `render` has been called, returns shallowly rendered output. You can then begin to assert facts about the output. For example, if your component's render method returns: