Fix the CellBroadcastSettings can't be searched.

If SettingsIntelligence does not set the target sdk,
it can't find the CellBroadcastSearchIndexableProvider.

Fixes: 154174082
Test: manual test the search result

Change-Id: I790a152a091064b19e1aced61ab2c640626a8e8e
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 5b0bd6a..6e91ece 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -25,6 +25,8 @@
     <uses-permission android:name="android.permission.MODIFY_PHONE_STATE" />
     <uses-permission android:name="android.permission.MANAGE_FINGERPRINT" />
 
+    <uses-sdk android:targetSdkVersion="23" />
+
     <application
         android:label="@string/app_name_settings_intelligence"
         android:icon="@mipmap/ic_launcher"