refactor: Refactor calculations and remove unused function in `uopool…

…/utils.rs`

- Removed commented out code for calculating `word_cost`
- Simplified calculation of `word_cost` by removing unnecessary division
- Added comments to explain the purpose of each calculation in the `calculate_pre_verification_gas()` function
- Removed unused function `calculate_valid_gas()` in the `utils.rs` file in the `uopool` crate.

crates/uopool/src/utils.rs

@@ -80,12 +80,6 @@ impl Overhead {
                 .saturating_mul(U256::from(uo_pack.len() + 31)),
             U256::from(32),
         );
-        // let word_cost = self
-        //     .per_user_op_word
-        //     .saturating_mul(U256::from(word_len))
-        //     .checked_div(U256::from(32))
-        //     .unwrap_or_default()
-        //     .saturating_add(rounding_const_word_cost);
 
         // fixed / bundle_size
         // -> fixed / bundle_size + rounding_const