Remove some dead code (#4)

* Remove balances storage slot, which is unused.

* Remove usused struct.

contracts/src/main.sw

@@ -91,11 +91,6 @@ struct RemoveLiquidityParams {
     deadline: u64,
 }
 
-struct RemoveLiquidityReturn {
-    eth_amount: u64,
-    token_amount: u64,
-}
-
 struct SwapWithMinimumParams {
     min: u64,
     deadline: u64,
@@ -132,8 +127,7 @@ abi Exchange {
 
 /// Storage delimited
 const S_DEPOSITS: b256 = 0x0000000000000000000000000000000000000000000000000000000000000000;
-const S_BALANCES: b256 = 0x0000000000000000000000000000000000000000000000000000000000000001;
-const S_TOTAL_SUPPLY: b256 = 0x0000000000000000000000000000000000000000000000000000000000000002;
+const S_TOTAL_SUPPLY: b256 = 0x0000000000000000000000000000000000000000000000000000000000000001;
 
 ////////////////////////////////////////
 // Helper functions
@@ -145,11 +139,6 @@ fn key_deposits(a: Address, asset_id: b256) -> b256 {
     hash_pair(S_DEPOSITS, inner, HashMethod::Sha256)
 }
 
-/// Compute the storage slot for an address's balance.
-fn key_balances(delim: b256, a: Address) -> b256 {
-    hash_pair(S_BALANCES, a.into(), HashMethod::Sha256)
-}
-
 /// Pricing function for converting between ETH and Tokens.
 fn get_input_price(input_amount: u64, input_reserve: u64, output_reserve: u64) -> u64 {
     assert(input_reserve > 0 && output_reserve > 0);