Remove FF create_deployment_only_for_processable_jobs

What does this MR do and why?

This removes the Feature Flag introduced in !132835 (merged) and fully enables the associated change.

Screenshots or screen recordings

This is already enabled globally in production:

How to set up and validate locally

N/A

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 #427062 (closed)