Do not track creations in gitlab_subscription_histories

What does this MR do?

Removes tracking previous state for creations of new rows in gitlab_subscriptions in gitlab_subscription_histories.

• They are mostly empty except created_at date.
• We know what's in created_at date even if the row is updated or destroyed later because we track the last two and created_at never changes
• This is an iteration to reduce space and improve performance.

This will be removed WIP after the data team approves it.

Issue #42546 (closed)

Screenshots

N/A

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team