Remove TODO related to adding assert from Sparse Tensor Pipeline code

Removing the TODO related to asserting that original `pm` is for ModuleOp.
The TODO is removed for following reasons:
1. There is no easy way to do this. We currently don't have this information stored in OpPassManager object.
2. There are currently no consumers of this information and storing this information with OpPassManager for a
   simple assert will be an overkill.

Reviewed By: aartbik

Differential Revision: https://reviews.llvm.org/D132699