docs: remove "Keeping your fork up-to-date" section
docs: remove "Keeping your fork up-to-date" section

It is not perfect. Updating develop branch only does not make sense.
workflow.md explains details.

ytetsuro/CodeIgniter4,kenjis/CodeIgniter4,lonnieezell/CodeIgniter4,samsonasik/CodeIgniter4,lonnieezell/CodeIgniter4,ytetsuro/CodeIgniter4,kenjis/CodeIgniter4,lonnieezell/CodeIgniter4,lonnieezell/CodeIgniter4,bcit-ci/CodeIgniter4,ytetsuro/CodeIgniter4,bcit-ci/CodeIgniter4,samsonasik/CodeIgniter4,lonnieezell/CodeIgniter4,lonnieezell/CodeIgniter4,ytetsuro/CodeIgniter4,kenjis/CodeIgniter4,samsonasik/CodeIgniter4,kenjis/CodeIgniter4,samsonasik/CodeIgniter4,ytetsuro/CodeIgniter4,samsonasik/CodeIgniter4,bcit-ci/CodeIgniter4,kenjis/CodeIgniter4,samsonasik/CodeIgniter4,bcit-ci/CodeIgniter4,bcit-ci/CodeIgniter4,ytetsuro/CodeIgniter4