Update updated_at when Todo state changes

What does this MR do?

This MR makes sure that we update the updated_at column for the Todo model. I'm adding ~backstage label since this change is not visible to the user.

Reason: update_all doesn't bump the updated_at timestamp.

Issue that depends on this MR: #214283 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides