Log Message:
Update gsettings-desktop-schemas to 3.6.0

* Change default list of input sources to be empty, so the
  default layout is inherited from the current settings
* Add option to show all the available input sources in the UI
* Add xkb-options key to input-sources
* Add colour saturation setting for the magnifier
* Change default keyboard shortcut for "Maximise"
* Add show-notifications setting (#677640)
* Change the default mouse-button-modifier to Super (#607797)
* Add brightness and contrast preferences (#645665)
* Add input-sources schema (#676101)
* Translation updates