[mlir][polynomial] remove incorrect canonicalization rule (#110318)

arith.add for tensor does not mod coefficientModulus, and it may
overflow; the result could be incorrect

It should be rewritten as modular arithmetic instead of arith

Revert https://github.com/llvm/llvm-project/pull/93132
Addresses https://github.com/google/heir/issues/749

Cc @j2kun