Update part2a.md

Fix App.js file extension to App.jsx

Author: juusosar

src/content/2/en/part2a.md

@@ -578,7 +578,7 @@ Note that this part has more exercises than the ones before, so <i>do not submit
 
 <h4>2.1: Course information step 6</h4>
 
-Let's finish the code for rendering course contents from exercises 1.1 - 1.5. You can start with the code from the model answers. The model answers for part 1 can be found by going to the [submission system](https://studies.cs.helsinki.fi/stats/courses/fullstackopen), clicking on <i>my submissions</i> at the top, and in the row corresponding to part 1 under the <i>solutions</i> column clicking on <i>show</i>. To see the solution to the <i>course info</i> exercise, click on _App.js_ under <i>courseinfo</i>.
+Let's finish the code for rendering course contents from exercises 1.1 - 1.5. You can start with the code from the model answers. The model answers for part 1 can be found by going to the [submission system](https://studies.cs.helsinki.fi/stats/courses/fullstackopen), clicking on <i>my submissions</i> at the top, and in the row corresponding to part 1 under the <i>solutions</i> column clicking on <i>show</i>. To see the solution to the <i>course info</i> exercise, click on _App.jsx_ under <i>courseinfo</i>.
 
 **Note that if you copy a project from one place to another, you might have to delete the <i>node\_modules</i> directory and install the dependencies again with the command _npm install_ before you can start the application.**