Docs: Update the download link to the latest version

⚠ ️NOTE THAT THIS FORK IS MAINTAINED FOR CRITICAL BUG FIXES AFFECTING RUNNING COSTS ONLY. NO OTHER CONTRIBUTIONS WILL BE ACCEPTED. ⚠️

What critical bug this MR is fixing?

Docs update: update download link to latest version. This should reduce future support queries.

Prompted by Support ticket (ZD Internal link: https://gitlab.zendesk.com/agent/tickets/496913)

Three more similar tickets related to older versions: https://gitlab.zendesk.com/agent/tickets/495370 https://gitlab.zendesk.com/agent/tickets/494101 https://gitlab.zendesk.com/agent/tickets/493572 (This one went to an emergency call)

How does this change help reduce cost of usage? What scale of cost reduction is it?

In what scenarios is this change usable with GitLab Runner's docker+machine executor?