Add branch reference to checkout step (#2126)

Author: FidelusAleksander

.github/workflows/0-start-exercise.yml

@@ -34,6 +34,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+        with:
+          ref: main
 
       - name: Get response templates
         uses: actions/checkout@v4