CI: install numpy in test stage to ensure version

.github/workflows/main.yml

@@ -107,7 +107,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install build "coveralls>=3.0.0" "numpy${{ matrix.ver.np }}"
+          pip install build "coveralls>=3.0.0"
 
       - name: bleeding edge
         if: matrix.ver.np == '>=2.0.0rc1'
@@ -124,6 +124,7 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
+          pip install "numpy${{ matrix.ver.np }}"
           python -m pytest --cov gstools --cov-report term-missing -v tests/
           python -m coveralls --service=github