fix: remove useless helper function

Author: albertcht

src/Common/Common.php

@@ -30,23 +30,4 @@ public static function mysql_escape($fieldValue)
 
  return $fieldValue;
  }
-
- /**
- * Convert boolean values to 0 or 1.
- *
- * @param $fieldValue
- * @return array|string|bool|string[]|bool[]
- */
- public static function convertBoolean($fieldValue)
- {
- if (is_array($fieldValue)) {
- return array_map(__METHOD__, $fieldValue);
- }
-
- if (is_bool($fieldValue)) {
- return (int) $fieldValue;
- }
-
- return $fieldValue;
- }
 }