Removing all references to magic_quotes.

Description

After upgrading my installation to PHP7.4 deprecated error appeared through the webpanel's ajax popup regarding get_magic_quotes_gpc().

Motivation and Context

Currently PHP7.4 is the latest version of PHP and currently the requirements for sbpp is PHP 7.1+, which would imply 7.4 is acceptable.

Fix #635

How Has This Been Tested?

Once the changes were made, I had run through the full functionality of the webpanel. Since the changes are only made to the xajax script it won't effect anything critical.

Magic quotes havn't been a thing since PHP5.4, so the function get_magic_quotes_gpc() will always return false.
https://www.php.net/manual/en/function.get-magic-quotes-gpc.php

Screenshots (if appropriate):

null

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.