ci: upgrade actions/upload-artifact to v7

Updates 1 occurrence across 1 workflow file from v4 to v7.
v7 runs on Node 24; v4 runs on Node 20 which is
being deprecated on GitHub Actions runners.

See https://github.com/actions/upload-artifact/releases/tag/v7.0.0

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: andrewhsu

.github/workflows/transform-sdk-build.yml

@@ -46,7 +46,7 @@ jobs:
           GOTOOLCHAIN: auto
         run: go test -c -o ./wasm-integration-test
       - name: Upload integration test binary
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: wasm-integration-test
           path: src/transform-sdk/tests/wasm-integration-test