Make it clear in docs about Geo secrets

What does this MR do and why?

Describe in detail what your merge request does and why.

When running pre-upgrade checks, a customer noticed a secret on the primary site, not the secondary site. In case of failover, ensuring that the primary and secondary sites have the same secrets is good practice. The MR is to add a new step to upgrade steps and ensure that the secrets are identical in both secondary and primary sites.

Zendesk ticket (Internal Only) Slack discussion (Internal Only)

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