Update part4c.md

Add a note as to the status of the app at the end of part 4c section, so that students are aware what is expected.

Author: Sam Vitare

src/content/4/en/part4c.md

@@ -556,4 +556,6 @@ const noteSchema = new mongoose.Schema({
 
 You can find the code for our current application in its entirety in the <i>part4-8</i> branch of [this GitHub repository](https://github.com/fullstack-hy2020/part3-notes-backend/tree/part4-8).
 
+NOTE: At this stage, firstly, some tests will fail. We will leave fixing the tests to a non-compulsory exercise. Secondly, in the deployed notes app, the creating a note feature will stop working as user is not yet linked to the frontend.
+
 </div>