Assert length of input connections, instead of inputs when disconnecting steps

Inputs become runtime inputs due to:
```
        if "inputs" in step_dict:
            for input_dict in step_dict["inputs"]:
                step_input = model.WorkflowStepInput(step)
                ...
```
in galaxy.managers.workflows.WorkflowContentsManager.

I guess it is debatable whether we want to adjust the test
or WorkflowContentsManager for disconnected steps.
When exported to .ga these are exactly the same (minus uuid
differences).

Author: mvdbeek

test/integration/test_workflow_refactoring.py

@@ -120,6 +120,7 @@ def test_basic_refactoring_types(self):
         assert self._latest_workflow.step_by_label("new_param2").position["left"] == 2
 
         assert len(self._latest_workflow.step_by_label("first_cat").inputs) == 1
+        assert len(self._latest_workflow.step_by_label("first_cat").inputs[0].connections) == 1
         actions = [
             {
                 "action_type": "disconnect",
@@ -128,7 +129,8 @@ def test_basic_refactoring_types(self):
             }
         ]
         self._refactor(actions)
-        assert len(self._latest_workflow.step_by_label("first_cat").inputs) == 0
+        assert len(self._latest_workflow.step_by_label("first_cat").inputs) == 1
+        assert len(self._latest_workflow.step_by_label("first_cat").inputs[0].connections) == 0
 
         actions = [
             {