Update app.py

>some minor changes in tool code

app.py

@@ -17,7 +17,7 @@ def my_arxiv_tool(keyword:str, n:int)-> str: #it's import to specify the return
         keyword:a keyword related to research paper.
         n: number of research papers.
     """
-    url = f'http://export.arxiv.org/api/query?search_query=all:{keyword}&year=2002&start=0&max_results=1'
+    url = f'http://export.arxiv.org/api/query?search_query=all:{keyword}&year=2002&start=0&max_results={n}'
     data = urllib.request.urlopen(url)
     xml_string = data.read().decode('utf-8')