arrow

GH-37560 [Python][Documentation] Replacing confusing batch size from 128Ki to 128_000 (#37605)

### Rationale for this change

https://github.com/apache/arrow/issues/37560

### Are these changes tested? -> No

### Are there any user-facing changes? -> Documentation
* Closes: #37560

Authored-by: Arkadiusz Rudny <aru@trackunit.com>
Signed-off-by: AlenkaF <frim.alenka@gmail.com>