Bump actions/upload-artifact from 2 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 2 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v2...v4)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/ci.yml

@@ -42,7 +42,7 @@ jobs:
       - name: Run tests
         run: dotnet test --collect:"XPlat Code Coverage" 
       - name: Upload coverage
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: Code coverage ${{ matrix.os }}
           path: "**/coverage.cobertura.xml"
@@ -85,7 +85,7 @@ jobs:
       - name: Create packages
         run: dotnet pack --configuration Release --output ./packages
       - name: Upload a Build Artifact
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: NuGet packages
           path: packages/*.*