Make the fragment title can’t searchable

we shouldn't take users so deep into the settings IA because it's easy
to feel lost in settings after clicking on a result without additional
context.

Bug: 143055215
Test: robotest & manual
Change-Id: I337cb5ead31e1e4e7bf9be78132e90630f83ee43

res/xml/connected_devices.xml

@@ -17,7 +17,6 @@
 <PreferenceScreen
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:settings="http://schemas.android.com/apk/res-auto"
-    android:key="connected_devices_screen"
     android:title="@string/connected_devices_dashboard_title">
 
     <com.android.settings.slices.SlicePreference
@@ -57,6 +56,7 @@
             android:title="@string/previous_connected_see_all"
             android:icon="@drawable/ic_chevron_right_24dp"
             android:order="10"
+            settings:searchable="false"
             android:fragment="com.android.settings.connecteddevice.PreviouslyConnectedDeviceDashboardFragment"/>
     </PreferenceCategory>