Revert "Fixes #3987 - Add informations about the upgrade of Rudder to version 2.8"

This reverts commit 76b648a9f0e9236c21625b7891fc8c51980406b6.
Fixes #3987 - Add informations about the upgrade of Rudder to version 2.8
Merge pull request #32 from nperron/bug_3987/doc/add_upgrade_to_2_8_infos

Fixes #3987 - Add informations about the upgrade of Rudder to version 2.8