build: update actions/upload-artifact and actions/download-artifact (#1053)

Source-Link: googleapis/synthtool@280ddae
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:346ab2efb51649c5dde7756cbbdc60dd394852ba83b9bbffc292a63549f33c17

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:230f7fe8a0d2ed81a519cfc15c6bb11c5b46b9fb449b8b1219b3771bcb520ad2
-# created: 2023-12-09T15:16:25.430769578Z
+  digest: sha256:346ab2efb51649c5dde7756cbbdc60dd394852ba83b9bbffc292a63549f33c17
+# created: 2023-12-14T22:17:57.611773021Z

.github/workflows/unittest.yml

@@ -26,9 +26,9 @@ jobs:
       run: |
         nox -s unit-${{ matrix.python }}
     - name: Upload coverage results
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
-        name: coverage-artifacts
+        name: coverage-artifact-${{ matrix.python }}
         path: .coverage-${{ matrix.python }}
 
   cover:
@@ -47,11 +47,11 @@ jobs:
         python -m pip install --upgrade setuptools pip wheel
         python -m pip install coverage
     - name: Download coverage results
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
-        name: coverage-artifacts
         path: .coverage-results/
     - name: Report coverage results
       run: |
-        coverage combine .coverage-results/.coverage*
+        find .coverage-results -type f -name '*.zip' -exec unzip {} \;
+        coverage combine .coverage-results/**/.coverage*
         coverage report --show-missing --fail-under=100