don't use mamba in deploy job (#66)

Author: jpn--

.github/workflows/run-tests.yml

@@ -126,17 +126,15 @@ jobs:
     - name: Install dependencies
       uses: conda-incubator/setup-miniconda@v3
       with:
-        miniforge-variant: Mambaforge
         miniforge-version: latest
-        use-mamba: true
         environment-file: envs/testing.yml
         python-version: "3.10"
         activate-environment: testing-env
         auto-activate-base: false
         auto-update-conda: false
     - name: Install Jupyterbook and ruamel.yaml
       run: |
-        mamba install jupyter-book ruamel.yaml sphinx-autosummary-accessors -c conda-forge
+        conda install jupyter-book ruamel.yaml sphinx-autosummary-accessors -c conda-forge
     - name: Install sharrow
       run: |
         python -m pip install --no-deps -e .