Used Php8 Construct But Still Need to Support 7.4

Author: oleibman

src/PhpSpreadsheet/Reader/Csv.php

@@ -649,14 +649,16 @@ public function getPreserveNullString(): bool
      * as escape Character.
      *
      * @param resource $stream
+     *
+     * @return array|false
      */
     private static function getCsv(
         $stream,
         ?int $length = null,
         string $separator = ",",
         string $enclosure = "\"",
         string $escape = "\\"
-    ): array|false {
+    ) {
         if (PHP_VERSION_ID >= 80400 && $escape !== '') {
             return @fgetcsv($stream, $length, $separator, $enclosure, $escape);
         }