gh-150885: Remove unused shutil._ensure_directory by gaborbernat · Pull Request #150883 · python/cpython

Introduced in python#8295 alongside shutil.unpack_archive() as a helper that
created the parent directory of each extracted member.

Orphaned by pythongh-146581 (pythonGH-146591), the ZIP path-traversal fix, which
reworked _unpack_zipfile() to create directories inline and deleted the
last _ensure_directory(targetpath) call site in the same change.

Since then the private helper has had no caller: a word-boundary search
across Lib, Modules, Python, Objects and Include finds zero references
outside its own definition, and a GitHub code search finds no downstream
importers.