incremement upload-artifact action version (#64)

As per https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/, version 3 of the upload-artifact action will be deprecated as of November 30th 2024. This change increments the version to 4.

.github/steps/3-upload-test-reports.md

@@ -30,7 +30,7 @@ To upload artifacts to the artifact storage, we can use an action built by GitHu
            npm install remark-cli remark-preset-lint-consistent vfile-reporter-json
            npx remark . --use remark-preset-lint-consistent --report vfile-reporter-json 2> remark-lint-report.json
 
-       - uses: actions/upload-artifact@v3
+       - uses: actions/upload-artifact@v4
          with:
            name: remark-lint-report
            path: remark-lint-report.json