article.py: correct data format

app/model/article.py

@@ -7,7 +7,7 @@ def add_article(content, source="manual_input", level="5", question="No question
         Article(
             text=content,
             source=source,
-            date=datetime.now().strftime("%-d %b %Y"),  # format style of `5 Oct 2022`
+            date=datetime.now().strftime("%d %b %Y"),  # format style of `5 Oct 2022`
             level=level,
             question=question,
         )