Bump actions/upload-artifact from 3.0.0 to 3.1.0 (JuliaLang#511)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 3.0.0 to 3.1.0.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@6673cd0...3cea537)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/exercise-tests.yml

@@ -58,7 +58,7 @@ jobs:
         run: julia --color=yes --project runtestrunner.jl
 
       - name: Upload reports as artifact
-        uses: actions/upload-artifact@6673cd052c4cd6fcf4b4e6e60ea986c889389535
+        uses: actions/upload-artifact@3cea5372237819ed00197afe530f5a7ea3e805c8
         with:
           name: test-reports
           path: ${{ steps.generate-reports.outputs.results-path }}