ci: Upgrade actions/upload-artifact and actions/download-artifact to v4 (#136)

Artifact actions v3 will be deprecated by December 5, 2024, updating
them.

cc paritytech/ci_cd#1078

Author: alvicsam

.github/workflows/review-trigger.yml

@@ -1,6 +1,6 @@
 name: Review-Trigger
 
-on: 
+on:
   pull_request_target:
     types:
       - opened
@@ -23,7 +23,7 @@ jobs:
           echo "Saving PR number: $PR_NUMBER"
           mkdir -p ./pr
           echo $PR_NUMBER > ./pr/pr_number
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         name: Save PR number
         with:
           name: pr_number