Fix Hardoded Configuration Editor Validation of File Upload Size

For almost every customer installation we are asked to increase the maximum upload size for files.

Editing the config.inc.php file (and apache/php configuration) allows vtiger to handle files larger than 5MB. But, due to the hardocoded figure in the Vtiger_NumberRange5_Validator_Js() class, it then becomes impossible to edit and save the Config Editor Screen without reducing the number to 5 again...