Remove the krunner widget from home screen by default

Because the widget does not have the text entry internally, and pops up a new window for entering search, which looks confusing and odd on the phone, we just don't add it by default for now until this can be fixed. This makes the first impression a bit better, and hides the annoyance behind needing to manually add the widget. Once the widget is fixed to not behave in such an odd manner, we can evaluate adding it back to the default layout.