fix(core): create_label test (testcontainers#771)

Make sure the test covers the intended behaviour. Previously it was
executing the create_labels function without actually verifying there
are no side effects.

Author: neykov

core/tests/test_labels.py

@@ -61,5 +61,5 @@ def test_session_are_module_import_scoped():
 def test_create_no_side_effects():
     input_labels = {"key": "value"}
     expected_labels = input_labels.copy()
-    create_labels("not-ryuk", {"key": "value"})
+    create_labels("not-ryuk", input_labels)
     assert input_labels == expected_labels, input_labels