upgrade download artifact action

Author: ghorbanzade

.github/workflows/main.yml

@@ -232,22 +232,22 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Download CppCon21 artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: cppcon21
           path: ${{ github.workspace }}
       - name: Download CppCon23 artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: cppcon23
           path: ${{ github.workspace }}
       - name: Download BazelCon23 artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: bazelcon23
           path: ${{ github.workspace }}
       - name: Download Web artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: web
           path: ${{ github.workspace }}