docs: clean up IP allow list URLs and security info re: data planes (#67074)

## What
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This is minor docs cleanup after we released the Iowa region on GCP.
There's not much to update, but it did prompt me to take a look at a few
things, update some URLs, and reframe the discussion of how Airbyte is
deployed to Cloud.

Companion change to this UI update, but there is no dependency between
them. https://github.com/airbytehq/airbyte-platform-internal/pull/17923

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## Can this PR be safely reverted and rolled back?
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- [x] YES 💚
- [ ] NO ❌

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docs/integrations/sources/postgres/cloud-sql-postgres.md

@@ -61,7 +61,7 @@ If you are on Airbyte Cloud, you will always need to modify your database config
 
    ![Add a Network](./assets/airbyte_cloud_sql_postgres_add_network.png)
 
-2. Add a new network, and enter the Airbyte's IPs, which you can find in our [Airbyte Security documentation](../../../platform/operating-airbyte/security#network-security-1).
+2. Add a new network, and enter the Airbyte's IPs, which you can find in our [Airbyte Security documentation](../../../platform/operating-airbyte/ip-allowlist).
 
 Now, click `Set up source` in the Airbyte UI. Airbyte will now test connecting to your database. Once this succeeds, you've configured an Airbyte Postgres source!