Update MembersTrackingDataTable.php (#715)

Updated the DataTables search to no longer use a multi-dimensional array which errors out.  This change fixes the search for Corporation\Intel and therefore fixes eveseat/seat#929

Author: Raikia

src/Http/DataTables/Corporation/Intel/MembersTrackingDataTable.php

@@ -104,7 +104,7 @@ public function ajax(): JsonResponse
                         });
                 }
 
-                $query->whereIn('character_id', $characters->toArray())
+                $query->whereIn('character_id', $characters->flatten(1))
                     ->orWhereHas('character', function ($query) use ($keyword) {
                         $query->where('name', 'like', "%{$keyword}%");
                     });