Revert "Disable coreutils on M1 Apple Silicon with arm64 (#2020)" (#2212)

This reverts commit 90d0d20508.

After further consideration, we've decided to remove this workaround:
* It only has an effect if the user has added `gnubin` from Homebrew Coreutils to PATH which is an unsupported setup
* It was intended to be applied only to a few select 3.8 and 3.9 versions that officially support Apple Silicon and only fail with Homebrew Coreutils in PATH because they have `config.*` from a too old version of Autoconf that doesn't support the Arm64 arch -- but
  * CPython devs [didn't actually fix the problem in 3.10, either, only in 3.11](https://github.com/pyenv/pyenv/pull/2157#issuecomment-968055387), so we'd need to apply it to all 3.10 releases, too
  * users started pushing this workaround into other unrelated branches because they were using the above unsupported setup. See https://github.com/pyenv/pyenv/pull/2190#pullrequestreview-835221952 for discussion.

plugins/python-build/share/python-build/3.9-dev

@@ -3,4 +3,4 @@ prefer_openssl11
 export PYTHON_BUILD_CONFIGURE_WITH_OPENSSL=1
 install_package "openssl-1.1.1k" "https://www.openssl.org/source/openssl-1.1.1k.tar.gz#892a0875b9872acd04a9fde79b1f943075d5ea162415de3047c327df33fbaee5" mac_openssl --if has_broken_mac_openssl
 install_package "readline-8.0" "https://ftpmirror.gnu.org/readline/readline-8.0.tar.gz#e339f51971478d369f8a053a330a190781acb9864cf4c541060f12078948e461" mac_readline --if has_broken_mac_readline
-install_git "Python-3.9-dev" "https://github.com/python/cpython" 3.9 arm64_apple_disable_homebrew_coreutils standard verify_py39 copy_python_gdb ensurepip
+install_git "Python-3.9-dev" "https://github.com/python/cpython" 3.9 standard verify_py39 copy_python_gdb ensurepip