call-datetime-without-tzinfo comment (#6105)
## Summary
Updated doc comment for `call_datetime_without_tzinfo.rs`. Online docs
also benefit from this update.
## Test Plan
Checked docs via
[mkdocs](https://github.com/astral-sh/ruff/blob/389fe13c934fe73679474006412b1eded4a2cad0/CONTRIBUTING.md?plain=1#L267-L296)
