github/workflows/tests: Update actions/upload-artifact to @v4

See: https://github.blog/changelog/2024-02-13-deprecation-notice-v1-and-v2-of-the-artifact-actions/
See: https://github.blog/news-insights/product-news/get-started-with-v4-of-github-actions-artifacts/

.github/workflows/tests.yml

@@ -53,7 +53,7 @@ jobs:
       - name: Build
         run: cd tests/inst && cargo build --verbose --release
       - name: Upload binary
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: ostree-test
           path: tests/inst/target/release/ostree-test
@@ -91,7 +91,7 @@ jobs:
           ./configure --with-curl --with-selinux --with-dracut=yesbutnoconf --with-composefs &&
           make -j 4 && make install DESTDIR=$(pwd)/install && tar -c -C install --zstd -f inst.tar.zst .
       - name: Upload binary
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: inst.tar.zst
           path: inst.tar.zst