Update hudi-testing-data.md
stock_ticks_cow should be stock_ticks_cown
The archive file `hudi-testing-data.zip` contains data files for 4 Hudi tables.
- `stock_ticks_cow`: a partitioned copy-on-write table
-- `stock_ticks_cow`: a non-partitioned copy-on-write table,
+- `stock_ticks_cown`: a non-partitioned copy-on-write table,
- `stock_ticks_mor`: a partitioned merge-on-read table
- `stock_ticks_morn`: a non-partitioned merge-on-read table;
