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] <support@github.com>

.github/workflows/ci.yml

@@ -84,15 +84,15 @@ jobs:
         bake run --build-version 1.0.$REVISION
 
     - name: Upload NuGet packages
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       if: success() || failure()
       with:
         name: packages
         path: "**/*nupkg"
         if-no-files-found: error
 
     - name: Upload test results
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       if: success() || failure()
       with:
         name: test-results

.github/workflows/release.yml

@@ -84,7 +84,7 @@ jobs:
         bake run --convention=Release --build-version 1.0.$REVISION --destination="nuget>github,nuget,release>github"
 
     - name: Upload test results
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       if: success() || failure()
       with:
         name: test-results