Use python -m pip invocation instead

Co-authored-by: Saransh Chopra <[email protected]>

.github/workflows/run_periodic_tests.yml

@@ -193,10 +193,10 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Install PyBaMM
-        run: pip install -e .
+        run: python -m pip install -e .
 
       - name: Test pybamm_install_odes on ${{ matrix.os }}
         run: |
-          pip cache purge
-          pip install wget cmake
+          python -m pip cache purge
+          python -m pip install wget cmake
           pybamm_install_odes