[BUG] anaconda-project prepare doesn't recognize osx-arm64 platform

[mattkram]

ALL software version info

$ conda --version
conda 4.12.0

$ anaconda-project --version
0.10.2

Mac OS 12.1

Description of expected behavior and the observed behavior

anaconda-project doesn't recognize M1 packages for osx-arm64 platform.

Relevant configuration files

name: bug
packages:
- python=3.8
platforms:
- osx-arm64

Complete, minimal, self-contained example code that reproduces the issue

anaconda-project prepare

Command output and/or screenshots of the bug in action

Potential issues with this project:
  * anaconda-project.yml: Unusual platform name 'osx-arm64' may be a typo (more usual examples: linux-64, osx-64, win-64)

[AlbertDeFusco]

fixed by #352