minor: remove unused _shutil_rmtree_remove_writable
minor: remove unused _shutil_rmtree_remove_writable

nicoddemus/pytest,txomon/pytest,nicoddemus/pytest,tomviner/pytest,The-Compiler/pytest,Akasurde/pytest,hackebrot/pytest,pytest-dev/pytest,tomviner/pytest,RonnyPfannschmidt/pytest,The-Compiler/pytest,alfredodeza/pytest,markshao/pytest