Updated artifact action

Author: LauraBoenchenLB

.github/workflows/model-training.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Train model
         run: python src/train.py
       - name: Upload trained model
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: regressor_mpg.pickle
           path: data/models/regressor_mpg.pickle