Update information on the fork

gui: Remove remaining in-app and meta social link references (ryujinx…

…-mirror#22)

* Migrate all GH references to `github.com/ryujinx-mirror`

* AboutWindow social references

gui: Disable usage of updater module for the time being (ryujinx-mirr…

…or#20)

And now I forgot about create_macos_build_headless 😅