De-duplication of Sidekiq information

What does this MR do?

There is some duplication of default instance values between the .com settings page and the administer documentation.

If a self-managed setting changes, we need to update it in both the admin pages and the .com settings page, despite it not affecting .com. It makes sense to remove the defaults from that page, and link back to the SSoT for each setting i.e. the admin documentation.

In this case, the Sidekiq memory killer environment variable default values are duplicated between the Sidekiq section of the .com settings page, and the Sidekiq memory killer documentation.

This MR de-duplicates the Sidekiq environment variable default values.

Related issues

#347004 (closed)

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