CI: Use conda-forge to create Python 3.10 env (pandas-dev#44388)

Author: lithomas1

.github/workflows/sdist.yml

@@ -53,6 +53,7 @@ jobs:
     - uses: conda-incubator/setup-miniconda@v2
       with:
         activate-environment: pandas-sdist
+        channels: conda-forge
         python-version: '${{ matrix.python-version }}'
 
     - name: Install pandas from sdist