fetch the phpcbf package directly from github

[bystrano]

The phpcbf package is not available on Melpa anymore, it needs to be fetched from Github.

[duianto]

There is another PR:
[+layer/php] Fix missed packages #14581

That proposes removing the two unmaintained php packages:

• phpcbf
• php-auto-yasnippet

I don't know if it's better to get them from their archived github pages,
or to remove them from the php layer.

There's an open issue about it here:
Packages 'php-auto-yasnippet' and 'phpcbf' in php layer unavailable #14381

[bystrano]

After giving this more thought, I think this package should be removed from spacemacs.

It is a wrapper around a formatting tool. But code formatting is also provided by LSP, which has better support and is the way forward.
Keeping this package in spacemacs would duplicate functionality.