TextEditor: add text cursor to assist interface

This will allow us to request assistance for a specific selection
instead of just the position.

Change-Id: Ib8e5b32d4a8f2936e5a6f1b7ac968d7f1d8d9de6
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/cppeditor/cppeditorwidget.cpp

@@ -1312,7 +1312,6 @@ AssistInterface *CppEditorWidget::createAssistInterface(AssistKind kind, AssistR
             return cap->createAssistInterface(textDocument()->filePath(),
                                               this,
                                               features,
-                                              position(),
                                               reason);
         } else {
             return TextEditorWidget::createAssistInterface(kind, reason);