Revert^2 "Nullability Annotations replacement"

This reverts commit 19d1d3d15d.

Reason for revert: revert it because this is not the root cause.

bug: 316867690
Change-Id: I0f168dbb64044aa720202af7b1040afd4f028c9c

src/com/android/settings/applications/credentials/DefaultCombinedPicker.java

@@ -16,7 +16,6 @@
 
 package com.android.settings.applications.credentials;
 
-import android.annotation.Nullable;
 import android.app.Activity;
 import android.app.settings.SettingsEnums;
 import android.content.Context;
@@ -38,6 +37,7 @@ import android.text.Html;
 import android.text.TextUtils;
 import android.util.Log;
 
+import androidx.annotation.Nullable;
 import androidx.core.content.ContextCompat;
 import androidx.preference.Preference;