Fix the notations for dynamic_update_slice and dynamic_slice (#1040)

`adjusted_start_indices` seems like a 1-d tensor from the type of
`shape(operand)` in `clamp(0, start_indices, shape(operand)
-slice_sizes)`.

docs/spec.md

@@ -2293,7 +2293,7 @@ the slice starting at `start_indices` is updated with the values in `update`.
 
 More formally, `result[i0, ..., iR-1]` is defined as:
 
-* `update[j0, ..., jR-1]` if `jd = adjusted_start_indices[d][] + id` where
+* `update[j0, ..., jR-1]` if `id = adjusted_start_indices[d][] + jd` where
   `adjusted_start_indices =
   clamp(0, start_indices, shape(operand) - shape(update))`.
 * `operand[i0, ..., iR-1]` otherwise.