remove reserve, as its perf impact is minimal

src/heap.rs

@@ -1,5 +1,5 @@
 use crate::instruction_handlers::HeapInterface;
-use std::ops::{Index, IndexMut, Range};
+use std::ops::{Index, Range};
 use u256::U256;
 use zkevm_opcode_defs::system_params::NEW_FRAME_MEMORY_STIPEND;
 
@@ -20,12 +20,6 @@ impl HeapId {
 #[derive(Debug, Clone, PartialEq)]
 pub struct Heap(Vec<u8>);
 
-impl Heap {
-    pub fn reserve(&mut self, additional: usize) {
-        self.0.reserve_exact(additional);
-    }
-}
-
 impl HeapInterface for Heap {
     fn read_u256(&self, start_address: u32) -> U256 {
         self.read_u256_partially(start_address..start_address + 32)
@@ -124,12 +118,6 @@ impl Index<HeapId> for Heaps {
     }
 }
 
-impl IndexMut<HeapId> for Heaps {
-    fn index_mut(&mut self, index: HeapId) -> &mut Self::Output {
-        &mut self.heaps[index.0 as usize]
-    }
-}
-
 impl PartialEq for Heaps {
     fn eq(&self, other: &Self) -> bool {
         for i in 0..self.heaps.len().max(other.heaps.len()) {