CI4 Download button should link to codeigniter4/framework

[kenjis]

Now it links to https://api.github.com/repos/codeigniter4/CodeIgniter4/zipball/v4.1.7
codeigniter4/CodeIgniter4 is the development repository.

See https://www.codeigniter.com/download

[MGatner]

@codeigniter4projects/website

[MGatner]

Pushed to production, confirmed the download link is now correct.

[kenjis]

Finally! Thanks.

[MGatner]

Now that the automated deposit script appears to be working we should be able to have a much faster release pipeline. Anything that needs to go live just becomes a PR from develop => master.