Change hash code for worksheet branch release1291 (#4306)

* Change hash code for worksheet

Backport of [PR #4207](https://github.com/PHPOffice/PhpSpreadsheet/pull/4207)

* Retitling Cloned Worksheets

Backport of PR #4302

* Make Test Php7.4 Compatible

tests/PhpSpreadsheetTests/Shared/StringHelperInvalidCharTest.php

@@ -40,5 +40,6 @@ class StringHelperInvalidCharTest extends TestCase
                 $sheet->getCell("A$row")->getValue()
             );
         }
+        $spreadsheet->disconnectWorksheets();
     }
 }