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/tap_screen_gesture_settings.xml

@@ -18,7 +18,6 @@
 <PreferenceScreen
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:key="gesture_tap_screen"
     android:title="@string/ambient_display_tap_screen_title">
 
     <com.android.settings.widget.VideoPreference
@@ -34,4 +33,4 @@
         app:controller="com.android.settings.gestures.TapScreenGesturePreferenceController"
         app:allowDividerAbove="true" />
 
-</PreferenceScreen>
+</PreferenceScreen>