Gitaly gameday template updates

What

Updates the Gitaly zonal change template to be more concise related to the change that's actually being made, Gameday vs Production outage recovery.

Why

The current template has a mix of gameday vs not-gameday steps mixed together, which can be slightly cumbersome to follow while executing the change. This introduces a little bit of redundancy in the step definitions, but I believe it will be ultimately easier to follow when it matters the most: at time of execution.