Remove ignore_column for dropped integrations.properties column

What does this MR do and why?

This MR is part of a sequence, aimed at encrypting Integration.properties.

This is the very last stage, and is a ~"technical debt" chore, removing the ignore_column statement in app/models/integration.rb.

How to set up and validate locally

This should not change any behavior in any way.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #36385