fix: broken functionality if soft_delete is set to true

This commit fixes the broken functionality ("undefined column
__soft_deleted") when soft_delete is set to true in scout.php config.
The reason for this is the change in behavior of in_array from PHP 7 to
8. Specifically, in PHP 7, in_array($aKeyThatExists, $singleDimensionalArray)
returns TRUE, but the same call in PHP 8 would return FALSE).

This fixes #318.

Author: phanan

src/Engines/TNTSearchEngine.php

@@ -352,7 +352,7 @@ private function handleSoftDeletes($builder, $model)
          *
          * When no __soft_deleted statement is given return all entries
          */
-        if (!in_array('__soft_deleted', $this->builder->wheres)) {
+        if (!array_key_exists('__soft_deleted', $this->builder->wheres)) {
             return $builder->withTrashed();
         }