Remvoe explicit choice of build parallelization (#142)

Author: schnellerhase

.github/workflows/test_mpc.yml

@@ -102,7 +102,7 @@ jobs:
       - name: Install DOLFINx-MPC (C++)
         run: |
           cmake -G Ninja -B build-dir -DCMAKE_BUILD_TYPE=${MPC_BUILD_MODE} -DCMAKE_CXX_FLAGS="${MPC_CMAKE_CXX_FLAGS}" -S cpp/
-          cmake --build build-dir --parallel 3
+          cmake --build build-dir
           cmake --install build-dir
 
       - name: Install DOLFINx-MPC (Python)