Explicitly mark the TopIntroPreference not searchable

Bug: 353847080
Test: Manually. Add screen recording to the bug
Test: atest AccessibilityHearingAidsFragmentTest
Flag: com.android.settings.accessibility.fix_a11y_settings_search
Change-Id: I7bdeb07d78ed717abf0aee53bc63952edb183354

res/xml/accessibility_hearing_aids.xml

@@ -20,7 +20,8 @@
     android:title="@string/accessibility_hearingaid_title">
 
     <com.android.settingslib.widget.TopIntroPreference
-        android:title="@string/accessibility_hearingaid_intro" />
+        android:title="@string/accessibility_hearingaid_intro"
+        settings:searchable="false" />
 
     <PreferenceCategory
         android:key="available_hearing_devices"

tests/robotests/src/com/android/settings/accessibility/AccessibilityHearingAidsFragmentTest.java

@@ -51,6 +51,7 @@ import org.robolectric.annotation.Config;
 import org.robolectric.shadow.api.Shadow;
 
 import java.util.List;
+import java.util.Objects;
 
 /** Tests for {@link AccessibilityHearingAidsFragment}. */
 @RunWith(RobolectricTestRunner.class)
@@ -88,7 +89,9 @@ public class AccessibilityHearingAidsFragmentTest {
         mShadowBluetoothAdapter.addSupportedProfiles(BluetoothProfile.HEARING_AID);
 
         final List<String> niks = AccessibilityHearingAidsFragment.SEARCH_INDEX_DATA_PROVIDER
-                .getNonIndexableKeys(mContext);
+                .getNonIndexableKeys(mContext).stream()
+                .filter(Objects::nonNull)
+                .toList();
         final List<String> keys =
                 XmlTestUtils.getKeysFromPreferenceXml(mContext, R.xml.accessibility_hearing_aids);