Preserve `stablehlo.gather` requantize pattern to meet operand and result type constraint.
Preserve `stablehlo.gather` requantize pattern to meet operand and result type constraint.

github.com/openxla/stablehlo/blob/main/docs/spec.md#gatherix states `(C14) element_type(operand) = element_type(result)`.

This should be kept for `stablehlo.gather`, `stablehlo.slice`, and `stablehlo.gather_slice`.
