docs: fix subject typo and change 'charts' to 'checklist' in the audit file. (#2452)

subjects/user-experience/piscine-ux/music-on/README.md

@@ -25,7 +25,7 @@ Conduct a heuristic analysis on **one** of these websites:
 
 **Tips:**
 
-- Pay attention to the global aspect of the document. It must be clear, simple and easy to read. You can get inspiration [canva](https://www.canva.com/) but don’t overload your design with too much details!
+- Pay attention to the global aspect of the documents. It must be clear, simple and easy to read. You can get inspiration [canva](https://www.canva.com/) but don’t overload your design with too much details!
 
 **Resources:**
 

subjects/user-experience/piscine-ux/music-on/audit/README.md

@@ -8,9 +8,9 @@
 
 ###### Is the document clear, simple and easy to read?
 
-###### Is the chart duplicated?
+###### Is the checklist duplicated?
 
-###### Is the chart complete?
+###### Is the checklist complete?
 
 ###### Is the heuristic analysis done to a South American music label? (ask the student to confirm)