Restore links to gbdev.gg8.se that were changed to archive.org mirror links #614
Description
Some links to my forum were changed in a hurry to the archive.org mirror when the site was down briefly. However, the site is actively maintained and rarely goes down in the grand scheme of things. The site also loads faster than archive.org which is notoriously slow. These are the relevant links.
src/HuC3.md:- Source: [GBDev Forums thread](https://web.archive.org/web/20231003224822/https://gbdev.gg8.se/forums/viewtopic.php?id=744)
src/MBC6.md:- Source: [GBDev Forums thread by endrift](https://web.archive.org/web/20241204030511/https://gbdev.gg8.se/forums/viewtopic.php?id=544)
src/MBC7.md:- Source: [GBDev Forums thread by endrift](https://web.archive.org/web/20250424080817/https://gbdev.gg8.se/forums/viewtopic.php?id=448)