Replace PHPExcel with PHPSpreadsheet

Testing scenario 1 Login as admin Go to  http://yourmoodleurl/lib/tests/other/spreadsheettestpage.php  and generate the Excel sample file. Review the server error logs to make sure there are no notices there. Open the Excel sample file in various office suites. CHECK the content is displayed as expected. You can download the ODS file and compare with it or download the Excel file without that patch. Alternatively, you can also compare to the moodletest_withoutthepatch.xlsx  attached file (which was created without the patch).   Testing scenario 2 Login as admin. Create a course with some enrolled students and one graded activity for some of them (at least). Access to the course. Go to Participants. Select all users and in the "With selected users" list choose "Download table data as Microsoft Excel (.xslx)". CHECK the file is downloaded and contains one row per user and, at least, the following columns:  "First name", "Surname" and "Email address". Go to Grades / Export / Excel spreadsheet Click over the Download button CHECK the file is downloaded and contains one row per user and, at least, the following columns:  "First name", "Surname", "ID number", "Institution", "Department", "Email address", "Course total", "Last downloaded from this course" and one column for each activity.