Update actions/checkout version

Author: FidelusAleksander

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

@@ -33,12 +33,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: main
 
       - name: Get response templates
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: skills/exercise-toolkit
           path: exercise-toolkit