Switch freeze guidance to not be a directive
MODIFY
repo2docker/buildpacks/conda/freeze.py
repo2docker/buildpacks/conda/freeze.py
"""
Freeze the conda environment.yml
-Run in a continuumio/miniconda3 image to ensure portability
+It runs the freeze in a continuumio/miniconda3 image to ensure portability
Usage:

Switch freeze guidance to not be a directive