fix: missing parenthesis in comment (#280)

zk_prover/src/chips/merkle_sum_tree.rs

@@ -20,8 +20,8 @@ pub struct MerkleSumTreeConfig {
 /// Chip that performs various constraints related to a Merkle Sum Tree data structure such as:
 ///
 /// * `s * swap_bit * (1 - swap_bit) = 0` (if `bool_and_swap_selector` is toggled). It basically enforces that swap_bit is either a 0 or 1.
-/// * `s * (element_r_cur - element_l_cur) * swap_bit + element_l_cur - element_l_next = 0` (if `bool_and_swap_selector` is toggled).
-/// * `s * (element_l_cur - element_r_cur) * swap_bit + element_r_cur - element_r_next = 0` (if `bool_and_swap_selector` is toggled).
+/// * `s * ((element_r_cur - element_l_cur) * swap_bit + element_l_cur - element_l_next) = 0` (if `bool_and_swap_selector` is toggled).
+/// * `s * ((element_l_cur - element_r_cur) * swap_bit + element_r_cur - element_r_next) = 0` (if `bool_and_swap_selector` is toggled).
 /// These 2 constraints enforce that if the swap_bit is equal to 1, the values will be swapped on the next row. If the swap_bit is equal to 0, the values will not be swapped on the next row.
 /// * `s * (left_balance + right_balance - computed_sum)`. It constraints the computed sum to be equal to the sum of the left and right balances (if `sum_selector` is toggled).