Tests: Workaround for Swig 4.2.1 != None erorrs

Works around the swig 4.2.1 x != None errors in the pyflamegpu test suite by using the more idiomatic is not None.

The underlying issue within Swig is resolved in 4.3.0.

tests/python/simulation/test_RunPlan.py

@@ -10,7 +10,7 @@ def test_constructor(self):
         model = pyflamegpu.ModelDescription("test")
         plan = None
         plan = pyflamegpu.RunPlan(model)
-        assert plan != None
+        assert plan is not None
         plan = None
 
     def test_setRandomSimulationSeed(self):

tests/python/simulation/test_RunPlanVector.py

@@ -23,7 +23,7 @@ def test_constructor(self):
         # Use New
         initialLength = 4
         plans = pyflamegpu.RunPlanVector(model, initialLength)
-        assert plans != None
+        assert plans is not None
         assert plans.size() == initialLength
         # Run the destructor
         plans = None

tests/python/simulation/test_cuda_ensemble.py

@@ -72,7 +72,7 @@ def test_constructor(self):
         # Use the ctor
         # explicit CUDAEnsemble(const ModelDescription& model, int argc = 0, const char** argv = None)
         ensemble = pyflamegpu.CUDAEnsemble(model, [])
-        assert ensemble != None
+        assert ensemble is not None
         # Check a property
         assert ensemble.Config().timing == False
         # Run the destructor ~CUDAEnsemble