ci: update upload-artifact and download-artifact actions to v4

v3 of `actions/upload-artifact` and `actions/download-artifact` will be
fully deprecated by 5 December 2024. Jobs that are scheduled to run
during the brownout periods will also fail. See [1][2].

[1]: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/
[2]: https://github.blog/changelog/2024-11-05-notice-of-breaking-changes-for-github-actions/

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

.github/workflows/ci.yml

@@ -39,7 +39,7 @@ jobs:
           mkdir -p /tmp/code_coverage
           go test ./... -short -cover -args "-test.gocoverdir=/tmp/code_coverage"
       - name: Upload code coverage artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: coverage-unit-${{ matrix.os }}-${{ github.run_id }}
           path: /tmp/code_coverage
@@ -100,7 +100,7 @@ jobs:
           mkdir -p /tmp/code_coverage
           ./scripts/run_integration_tests.sh
       - name: Upload code coverage artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: coverage-integration-${{ matrix.git-version }}-${{ github.run_id }}
           path: /tmp/code_coverage
@@ -200,7 +200,7 @@ jobs:
           go-version: 1.22.x
 
       - name: Download all coverage artifacts
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           path: /tmp/code_coverage