Remove second arg from on_selection_changed.

The deselected argument was unused, so remove it from the signal and
the slot.

qutebrowser/completion/completer.py

@@ -241,8 +241,8 @@ class Completer(QObject):
         else:
             return s
 
-    @pyqtSlot(QItemSelection, QItemSelection)
-    def on_selection_changed(self, selected, _deselected):
+    @pyqtSlot(QItemSelection)
+    def on_selection_changed(self, selected):
         """Change the completed part if a new item was selected.
 
         Called from the views selectionChanged method.

qutebrowser/completion/completionwidget.py

@@ -104,7 +104,7 @@ class CompletionView(QTreeView):
     """
 
     resize_completion = pyqtSignal()
-    selection_changed = pyqtSignal(QItemSelection, QItemSelection)
+    selection_changed = pyqtSignal(QItemSelection)
 
     def __init__(self, win_id, parent=None):
         super().__init__(parent)
@@ -255,7 +255,7 @@ class CompletionView(QTreeView):
     def selectionChanged(self, selected, deselected):
         """Extend selectionChanged to call completers selection_changed."""
         super().selectionChanged(selected, deselected)
-        self.selection_changed.emit(selected, deselected)
+        self.selection_changed.emit(selected)
 
     def resizeEvent(self, e):
         """Extend resizeEvent to adjust column size."""

tests/unit/completion/test_completer.py

@@ -216,6 +216,6 @@ def test_on_selection_changed(before, newtxt, count, quick_complete, after,
     _set_cmd_prompt(status_command_stub, before)
     # schedule_completion_update is needed to pick up the cursor position
     completer_obj.schedule_completion_update()
-    completer_obj.on_selection_changed(selection, None)
+    completer_obj.on_selection_changed(selection)
     model.data.assert_called_with(indexes[0])
     _validate_cmd_prompt(status_command_stub, after)