docs: Update index.md (#13306)

Update index.md

fixed

Author: wubx

docs/doc/14-sql-commands/00-ddl/50-udf/index.md

@@ -75,7 +75,7 @@ def gcd(x: int, y: int) -> int:
 
 if __name__ == '__main__':
     # create a UDF server listening at '0.0.0.0:8815'
-    server = UdfServer("0.0.0.0:8815")
+    server = UDFServer("0.0.0.0:8815")
     # add defined functions
     server.add_function(gcd)
     # start the UDF server
@@ -122,4 +122,4 @@ python3 udf_server.py
 
 ```sql
 CREATE FUNCTION gcd (INT, INT) RETURNS INT LANGUAGE python HANDLER = 'gcd' ADDRESS = 'http://0.0.0.0:8815'；
-```
+```