Fix Namespace Used to Lookup 'pgo-backrest-repo-config' Secret when Enabling S3 Support

[andrewlecuyer]

Updated the namespace being utilized to lookup the pgo-backrest-repo-config secret when enabling AWS S3 support for a cluster (specifically when creating the pgBackRest shared repo deployment). The Operator namespace is now utilized when looking up this secret (instead of the namespace for the cluster itself), in support of Ansible PGO installs where the pgo-backrest-repo-config secret is created in the Operator namespace only.

Checklist:

• Have you added an explanation of what your changes do and why you'd like them to be included?
• Have you updated or added documentation for the change, as applicable?
• Have you tested your changes on all related environments with successful results, as applicable?

Type of Changes:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

What is the current behavior? (link to any open issues here)
The wrong namespace (specifically the namespace of the cluster) is being utilized to lookup the pgo-backrest-repo-config secret when enabling AWS S3 support for a cluster (specifically when creating the pgBackRest shared repo deployment).

[ch4085]

What is the new behavior (if this is a feature change)?
The Operator namespace is now utilized when looking up this secret (instead of the namespace for the cluster itself), in support of Ansible PGO installs where the pgo-backrest-repo-config secret is created in the Operator namespace only.

Other information:
N/A