Breaking change: Support ending for runners Prior to 9.0

What this post added

This post announces the deprecation and eventual removal of support for GitLab Runner versions prior to 9.0. It states that runners older than 9.0 will stop working with GitLab 10.0 due to the removal of an old API. Users are strongly encouraged to upgrade their runners to version 9.0 or newer before GitLab 10.0 is released on September 22nd, with RC deployment around September 8th. Instructions are provided on how to check for old runners and how to upgrade them.