Bump actions/upload-artifact from 1 to 2.3.1

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 1 to 2.3.1.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v1...v2.3.1)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
           go-version: 1.15
       - uses: actions/checkout@v1
       - run: make build
-      - uses: actions/upload-artifact@v1
+      - uses: actions/upload-artifact@v2.3.1
         with:
           name: podsync-${{ matrix.os }}
           path: bin/