shebang typo in generate_legacy_storage_files.py
#### Problem description

The shebang line at the top of https://github.com/pandas-dev/pandas/blob/master/pandas/tests/io/generate_legacy_storage_files.py#L1 has an incorrect interpreter.

It is currently set to ```/usr/env/bin python```

#### Expected Output

The interpreter should instead be set to ```/usr/bin/env python```