DOC: clarify that `value_counts`, `sort_values`, `sort_index` etc. are deterministic

[cmp0xff]

Pandas version checks

• I have checked that the issue still exists on the latest versions of the docs on main here

Location of the documentation

https://pandas.pydata.org/docs/dev/reference/api/pandas.DataFrame.sort_values.html

Documentation problem

In the current dev documentation, it is not clear whether value_counts, sort_values, sort_index etc. give the same result in case of ties. It turns out the underlying sorting function is numpy.sort, and the answer is positive for quick sort, when one checkes the source.

Suggested fix for documentation

Since quicksort is the default sorting algorithm, we can clarify that the sorting is deterministic. Other algorithms might be clarified if numpy/numpy#30262 is resolved.

[makroumi]

I can take this and open a small docs PR to clarify the determinism of value_counts, sort_values, and sort_index in the presence of ties. I will reference this issue in the PR and keep the change docs-only and atomic.