Hide animation shown while the kernel is loading.

def _hide_loading_page(self):
        """Hide animation shown while the kernel is loading."""
        self.infowidget.hide()
        self.shellwidget.show()
        self.info_page = self.blank_page
        self.set_info_page()
        self.shellwidget.sig_prompt_ready.disconnect(self._hide_loading_page)