Incorrect class in documentation

Author: PowerKiKi

docs/topics/accessing-cells.md

@@ -385,7 +385,7 @@ $worksheet = $spreadsheet->getActiveSheet();
 // Get the highest row and column numbers referenced in the worksheet
 $highestRow = $worksheet->getHighestRow(); // e.g. 10
 $highestColumn = $worksheet->getHighestColumn(); // e.g 'F'
-$highestColumnIndex = \PhpOffice\PhpSpreadsheet\Cell\Cell::columnIndexFromString($highestColumn); // e.g. 5
+$highestColumnIndex = \PhpOffice\PhpSpreadsheet\Cell\Coordinate::columnIndexFromString($highestColumn); // e.g. 5
 
 echo '<table>' . "\n";
 for ($row = 1; $row <= $highestRow; ++$row) {