conda: also add -c defaults in workflow

Not sure why I missed that in 3fd35cf.
Anyway, it seems like the change only affected `conda build`, not `conda
install` (yet).

.github/workflows/conda.yaml

@@ -113,14 +113,14 @@ jobs:
       - name: Install/Test raw package
         if: inputs.package == 'raw'
         run: |
-          conda install -y pypdfium2_${{ inputs.package }} --override-channels -c ./conda_dist/ -c bblanchon
+          conda install -y pypdfium2_${{ inputs.package }} --override-channels -c ./conda_dist/ -c bblanchon -c defaults
           python conda/raw/minitest.py
       
       - name: Install/Test helpers package
         if: inputs.package == 'helpers'
         run: |
           conda install -y pytest pillow numpy
-          conda install -y pypdfium2_${{ inputs.package }} --override-channels -c ./conda_dist/ -c pypdfium2-team -c bblanchon
+          conda install -y pypdfium2_${{ inputs.package }} --override-channels -c ./conda_dist/ -c pypdfium2-team -c bblanchon -c defaults
           pytest tests/ tests_old/
   
   publish: