Update gitlab-runner links to main in docs

Steve Xuereb - Out of Office back 2026-01-05requested to merge
steveazz/update-gitlab-runner-default-branch into master

What does this MR do?

In gitlab-runner#27239 (closed) the default branch of GitLab Runner is going to change to main which already exists and being kept in sync with master until the full migration is done.

In some cases I've added /-/ path seperator to use the new URL structure in GitLab.

reference gitlab-runner#27239 (closed)

Edited by Steve Xuereb - Out of Office back 2026-01-05

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