Private Runner upgrade required for GitLab 11.10 MR pipelines

What this post added

Introduced an improvement to MR Pipelines in the 11.10 release that builds the combined ref (source + target branch) as part of the merge request pipeline. This requires users of private GitLab Runners on versions 11.8 or older to upgrade to 11.9 or newer to avoid an 'Your runner is outdated' error. Shared Runner fleet users are not impacted.