Update make release for dune-release.2.0.0

[mbarbin]

While cutting the release 2.0.0 I noticed a few things that needs updating in the make release script.

1. The option -n was renamed. I removed it, dune-release is now able to determine the package name from the opam file found at the root;
2. The work around for delegates is no longer necessary, I removed it;
3. Seeing that we do publish the doc in the gh-pages branch, I added the corresponding entry (publish doc)

As it stands, I believe the release sequence is very close to what dune-release does by default when invoked without arguments, but keeping the entries as a sequence allows to trouble shoot if a step fails, doing some sanity checks along the way, etc.

[mbarbin]

Note that the new version 2.1.0 of dune-release no longer has the option to publishing the doc to the gh-pages.

Nowadays, the recommendation is to simply point users to the documentation in ocaml.org directly. Locally I believe there exists other alternatives such as odig.

In the light of the dune-release change, I am inclined to delete the gh-pages and disable the GitHub pages for this project.

Objections?

cc @rgrinberg @emillon

[mbarbin]

TODO: investigate what further updates are required to use the latest dune-release.2.1.0.

[rgrinberg]

No objections from me