Merge pull request #4585 from Laravel-Backpack/refactor-datetime

remove deprecated strftime() in PHP 8.1

Author: tabacitu

src/resources/views/crud/fields/datetime.blade.php

@@ -9,7 +9,7 @@
 
 $timestamp = strtotime(old_empty_or_null($field['name'], '') ??  $field['value'] ?? $field['default'] ?? '');
 
-$value = $timestamp ? strftime('%Y-%m-%dT%H:%M:%S', $timestamp) : '';
+$value = $timestamp ? date('Y-m-d\TH:i:s', $timestamp) : '';
 @endphp
 
 @include('crud::fields.inc.wrapper_start')