Only download one file on sign cert

[reecebrowne]

Description

This is the only change, prettier has been a bit overzealous with quotes.
if (window.isDownloadScriptInitialized) return; // Prevent re-execution
window.isDownloadScriptInitialized = true;

Closes #()

Checklist

• [ X] I have read the Contribution Guidelines
• [ X] I have performed a self-review of my own code
• [ X] I have attached images of the change if it is UI based
• [ X] I have commented my code, particularly in hard-to-understand areas
• [ X] If my code has heavily changed functionality I have updated relevant docs on Stirling-PDFs doc repo
• [X ] My changes generate no new warnings
• [ X] I have read the section Add New Translation Tags (for new translation tags only)