WidgetExplorer: Do not auto focus the search field on tablet mode

On tablet mode, when opening Widget Explorer, the virtual keyboard will
be automatically opened, which makes the screen crowded. Only call
forceActiveFocus() when tablet mode is off.

BUG: 444716
2 jobs for !670 with widget-explorer-disable-focus-tablet-mode in 5 minutes and 14 seconds (queued for 56 minutes and 54 seconds)
latest merge request