Maintenance: update release process script (#1340)

Maintenance: update release process script (#1340)

* release notes no longer mention specific version since
  c0789db1f479206e43f96add370363127834757a. No more need to
  validate it is correct before release.

* web server has not been the direct release destination for
  many years. Remove mentions of $dst/changesets/

* web server references github repository for basic
  information. Do not push CONTRIBUTORS, COPYING, README,
  CREDITS and SPONSORS files to staging area.

* release notes no longer link to local ChangeLog file.
  No need to adjust the hyperlink.