Fix 2 Maintainability issues in main\downloadManager.js

[rustdevbtw]

CodeFactor found multiple issues:

'fileURL' is defined but never used.

• main\downloadManager.js:4

'downloadFile' is defined but never used.

• main\downloadManager.js:4

And why https://ovh.net/files/1Gio.dat (1GB in size) is downloaded?

@Patrick-web

[jdev082]

'defined but never used', that means they can just be deleted right?

[rustdevbtw]

@JaydenDev It's weird but true. Actually, the codebase is messy and needs a cleanup. Additionally, the new re-written version of Electron App Store would take some time to complete (as I'm working on it alone).