fix: install ngspice for python unit tests

.github/workflows/test_code.yml

@@ -27,6 +27,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
+          sudo apt install -y ngspice
           python -m pip install --upgrade pip
           pip install -r requirements.txt
           # pip install .