Update tier count for max registered runners

What does this MR do and why?

In a Reddit thread, there was some confusion around the maximum number of runners that could be registered for the free tier.

This change updates the field in the table to better distinguish that the total is not a summation for projects and group, but rather an individual allocation for each entity.

Screenshots or screen recordings

Before

After

How to set up and validate locally

Run the review app and checkout the table in the docs page.

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