Decrement numpy version to fix workflow tests

.github/workflows/tests.yml

@@ -27,7 +27,7 @@ jobs:
         python -m pip install --upgrade pip
         pip install flake8 pytest pytest-cov
         pip install -r requirements.txt
-        pip install numpy --upgrade
+        pip install numpy==1.26.4
     - name: Install CIM Optimizer
       run: |
         pip install -e ./cim_optimizer