Revert "Nullability Annotations replacement"

This reverts commit cf0501e4d7.

Reason for revert: b/317462033, it seems a flaky but revert it first.

Change-Id: Ie1d5e279cca6477fc17d8c27c1ecda8d7a6b2553

src/com/android/settings/core/CategoryMixin.java

@@ -19,6 +19,7 @@ package com.android.settings.core;
 import static androidx.lifecycle.Lifecycle.Event.ON_PAUSE;
 import static androidx.lifecycle.Lifecycle.Event.ON_RESUME;
 
+import android.annotation.Nullable;
 import android.content.BroadcastReceiver;
 import android.content.ComponentName;
 import android.content.Context;
@@ -29,7 +30,6 @@ import android.text.TextUtils;
 import android.util.ArraySet;
 import android.util.Log;
 
-import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import androidx.lifecycle.LifecycleObserver;
 import androidx.lifecycle.OnLifecycleEvent;

src/com/android/settings/core/PreferenceControllerListHelper.java

@@ -20,14 +20,13 @@ import static com.android.settings.core.PreferenceXmlParserUtils.METADATA_CONTRO
 import static com.android.settings.core.PreferenceXmlParserUtils.METADATA_FOR_WORK;
 import static com.android.settings.core.PreferenceXmlParserUtils.METADATA_KEY;
 
+import android.annotation.NonNull;
 import android.annotation.XmlRes;
 import android.content.Context;
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.util.Log;
 
-import androidx.annotation.NonNull;
-
 import com.android.settings.core.PreferenceXmlParserUtils.MetadataFlag;
 import com.android.settingslib.core.AbstractPreferenceController;
 

src/com/android/settings/core/PreferenceXmlParserUtils.java

@@ -16,6 +16,7 @@
 
 package com.android.settings.core;
 
+import android.annotation.NonNull;
 import android.annotation.XmlRes;
 import android.content.Context;
 import android.content.res.TypedArray;
@@ -27,7 +28,6 @@ import android.util.Log;
 import android.util.Xml;
 
 import androidx.annotation.IntDef;
-import androidx.annotation.NonNull;
 
 import com.android.settings.R;