push.yml: update the "upload-artifact" action to v7

Author: stephengold

.github/workflows/push.yml

@@ -21,7 +21,7 @@ jobs:
           ./gradlew -Pbt=Debug -Pflavor=Sp -Ptarget=Linux64 -Ptool=gcc -x checkstyleMain -x checkstyleTest build install \
             --console=plain
       - if: failure()
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: test-report
           path: build/reports/tests/test
@@ -378,7 +378,7 @@ jobs:
           ./gradlew -Pbt=Release -Pflavor=Sp -Ptarget=Linux64 build install \
             --console=plain
       - if: failure()
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: test-report
           path: build/reports/tests/test