chore: Update post_process_raw function in artifact.py

The post_process_raw function in artifact.py has been updated to set the raw value to "Built Successfully ✨" when the artifact type is unknown. This change improves the clarity of the code and provides a more meaningful message for unknown artifact types.

src/backend/base/langflow/schema/artifact.py

@@ -50,6 +50,6 @@ def post_process_raw(raw, artifact_type: str):
     if artifact_type == ArtifactType.STREAM.value:
         raw = ""
     elif artifact_type == ArtifactType.UNKNOWN.value:
-        raw = str(raw)
+        raw = "Built Successfully ✨"
 
     return raw