Updated github actions to use Mambaforge

- Per the workaround in "conda-incubator/setup-miniconda#274 (comment)"
- Set to use mamba over conda

.github/workflows/gh-ci.yaml

@@ -148,7 +148,8 @@ jobs:
           environment-file: docs/requirements.yaml
           add-pip-as-python-dependency: true
           architecture: x64
-          mamba-version: "*"
+          miniforge-variant: Mambaforge
+          uses-mamba: true
           channels: conda-forge, defaults
           activate-environment: cookiecutter-mdakit-docs
           auto-update-conda: true