Fix forgotten 'delete' calls at the end of some tests

Context

Fix simple direct leaks mentioned in aidge#196 (closed) where delete call was forgotten

aidge_backend_cpu/unit_tests/test_scheduler.py

@@ -17,12 +17,12 @@ class test_scheduler(unittest.TestCase):
 
         input_node = aidge_core.Producer(aidge_core.Tensor(values), "Input")
         relu = aidge_core.ReLU()
+        input_node.add_child(relu)
 
         gv = aidge_core.GraphView()
         gv.add(relu)
         gv.add(input_node)
 
-        input_node.add_child(relu)
 
         gv.set_datatype(aidge_core.dtype.int32)
         gv.set_backend("cpu")