pinning numpy for older SKL backwards compat tests (#780)

.github/workflows/pythonapp.yml

@@ -56,10 +56,10 @@ jobs:
         python -m pip install -e .[tests] -f https://download.pytorch.org/whl/torch_stable.html
     - name: Test with older SKLearn on Linux with py3.9 to check backward compatibility
       if: ${{ matrix.python-version == '3.9' && startsWith(matrix.os, 'ubuntu') == true }}
-      run: python -m pip install scikit-learn==1.2.1
+      run: python -m pip install scikit-learn==1.2.1 numpy==1.26.4
     - name: Pin SKLearn<1.5.0 on not Linux with py3.9
       if: ${{ !(matrix.python-version == '3.9' && startsWith(matrix.os, 'ubuntu') == true) }}
-      run: python -m pip install "scikit-learn<1.5.0"
+      run: python -m pip install "scikit-learn<1.5.0" numpy==1.26.4
     - name: Run basic tests without extra
       run: pytest
     - name: Coverage on basic tests without extra