Fix link to containerization question's answer (#5885)

Corrected content for Containerization question from stateless-http to containerization.

src/data/question-groups/backend/backend.md

@@ -61,7 +61,7 @@ questions:
     topics:
       - 'Beginner'
   - question: What is containerization, and how does it benefit backend development?
-    answer: statelessness-http.md
+    answer: containerization.md
     topics:
       - 'Beginner'
   - question: What measures would you take to secure a newly developed API?