Do not set default values for deprecated fdw settings

What does this MR do?

In !4491 (merged), we removed support for FDW. In addition we marked several settings as deprecated. However, we were setting default values to those deprecated settings, and that triggered deprecation warnings to users.

To reproduce, install 13.3.1 EE package, set only external_url, run reconfigure - you see a deprecation warning.

Checklist

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