test: verify note deletion by id instead of content

Author: AbelGAlem

src/content/4/en/part4b.md

@@ -1087,8 +1087,8 @@ describe('when there is initially some notes saved', () => {
 
       const notesAtEnd = await helper.notesInDb()
 
-      const contents = notesAtEnd.map(n => n.content)
-      assert(!contents.includes(noteToDelete.content))
+      const ids = notesAtEnd.map(n => n.id)
+      assert(!ids.includes(noteToDelete.id))
 
       assert.strictEqual(notesAtEnd.length, helper.initialNotes.length - 1)
     })