build(deps): bump actions/upload-artifact from 3 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v3...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/tests.yml

@@ -114,7 +114,7 @@ jobs: # Docs: <https://git.io/JvxXE>
         if: matrix.os == 'linux'
         run: ./error-pages --version && ./error-pages -h
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: error-pages-${{ matrix.os }}-${{ matrix.arch }}
           path: error-pages
@@ -175,7 +175,7 @@ jobs: # Docs: <https://git.io/JvxXE>
 
       - run: docker save app:ci > ./docker-image.tar
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: docker-image
           path: ./docker-image.tar