[actions] specify miniconda-version

Author: jgrewe

.github/workflows/pythonpackage.yml

@@ -58,6 +58,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: conda-incubator/setup-miniconda@v2
         with:
+          miniconda-version: "latest"
           activate-environment: deptest-${{ matrix.python-version }}
           python-version: ${{ matrix.python-version }}
           channels: conda-forge