Update main.yml

Author: teo9806

.github/workflows/main.yml

@@ -104,7 +104,7 @@ jobs:
         id: date
         run: echo "date=$(date +'%Y-%m-%dT%H_%M_%S')" >> $GITHUB_OUTPUT #no colons allowed for artifacts
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         if: always()
         with:
           name: unit_results_${{ matrix.python-version }}-${{ steps.date.outputs.date }}.csv