Remove unused imports in SecuritySettings.java

import java.util.Observable;

import java.util.Observer;

import android.app.Activity;

import android.app.AlertDialog;

import android.app.Dialog;

import android.app.admin.DevicePolicyManager;

import android.database.Cursor;

import android.location.LocationManager;

import android.os.Bundle;

import android.os.SystemProperties;

import android.preference.CheckBoxPreference;

import android.preference.ListPreference;

import android.preference.Preference;

import android.preference.PreferenceActivity;

import android.preference.PreferenceCategory;

import android.preference.PreferenceManager;

import android.preference.PreferenceScreen;

import android.preference.Preference.OnPreferenceChangeListener;

import android.provider.Settings;

import android.security.Credentials;

import android.security.KeyStore;

import android.telephony.TelephonyManager;

import android.util.Log;

import android.view.View;

import android.widget.TextView;

import android.widget.Toast;

package com.android.settings;

import static android.provider.Settings.System.SCREEN_OFF_TIMEOUT;

import android.content.BroadcastReceiver;

import android.content.ContentResolver;

import android.content.Context;