fix example of reading parquet from s3 (#896)

Author: sir-sigurd

examples/sql-parquet-s3.py

@@ -31,7 +31,7 @@
 
 ctx = datafusion.SessionContext()
 path = f"s3://{bucket_name}/"
-ctx.register_object_store(path, s3)
+ctx.register_object_store("s3://", s3, None)
 
 ctx.register_parquet("trips", path)