[Doc] tzdata error due to a lack of a discoverable system timezone database

### Describe the enhancement requested

Some timezone-dependent PyArrow tests require a discoverable system timezone database (tzdata / zoneinfo).

On environments without standard filesystem layouts (e.g. non-FHS compliant systems or minimal containers), these tests can fail with errors like:

```
ArrowInvalid: Cannot locate or parse timezone 'CET' discover_tz_dir failed to find zoneinfo
```

There have been several mitigations over time like older interim fixes for Windows itself (#36996), PR #45425, and recent Windows CI fixes such as commit https://github.com/apache/arrow/commit/ab2c0ad6b23d05d5f77fc8a34d5a1c4baaacb0a4.

Windows-specific failures appear to be largely handled now, but the underlying requirement and expected behavior are not documented for contributors on other platforms (e.g. non-FHS systems and hermetic environments).

Happy to follow up with a small documentation PR if this sounds reasonable. The goal would be to clarify that these failures are environment-related and expected in certain setups, rather than indicating a bug in Arrow itself.

### Component(s)

Documentation