Make balance_gradient preserved in export (#120332)
Summary: We can only not-decompose CompositeImplicit functional custom ops. From the looks of the implementation, this op looks functional. So the fix is just fixing the schema.
Test Plan: CI
Differential Revision: D54019265
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120332
Approved by: https://github.com/zhxchen17
