refactor(abstract-utxo): remove dead code altScriptHash and supportAltScriptDestination

These properties were set but never read anywhere in the BitGo codebase.
Removing them also eliminates the utxo-lib dependency from ltc.ts and tltc.ts.

Co-authored-by: Cursor <cursoragent@cursor.com>

TICKET: BTC-2650

Author: OttoAllmendinger

modules/abstract-utxo/src/abstractUtxoCoin.ts

@@ -400,8 +400,6 @@ export abstract class AbstractUtxoCoin
 {
   abstract name: UtxoCoinName;
 
-  public altScriptHash?: number;
-  public supportAltScriptDestination?: boolean;
   public readonly amountType: 'number' | 'bigint';
 
   protected constructor(bitgo: BitGoBase, amountType: 'number' | 'bigint' = 'number') {

modules/abstract-utxo/src/impl/ltc/ltc.ts

@@ -1,20 +1,11 @@
 import { BitGoBase } from '@bitgo/sdk-core';
-import * as utxolib from '@bitgo/utxo-lib';
 
 import { AbstractUtxoCoin } from '../../abstractUtxoCoin';
 import { UtxoCoinName } from '../../names';
 
 export class Ltc extends AbstractUtxoCoin {
   readonly name: UtxoCoinName = 'ltc';
 
-  constructor(bitgo: BitGoBase) {
-    super(bitgo);
-    // use legacy script hash version, which is the current Bitcoin one
-    this.altScriptHash = utxolib.networks.bitcoin.scriptHash;
-    // do not support alt destinations in prod
-    this.supportAltScriptDestination = false;
-  }
-
   static createInstance(bitgo: BitGoBase): Ltc {
     return new Ltc(bitgo);
   }

modules/abstract-utxo/src/impl/ltc/tltc.ts

@@ -1,5 +1,4 @@
 import { BitGoBase } from '@bitgo/sdk-core';
-import * as utxolib from '@bitgo/utxo-lib';
 
 import { UtxoCoinName } from '../../names';
 
@@ -8,12 +7,6 @@ import { Ltc } from './ltc';
 export class Tltc extends Ltc {
   readonly name: UtxoCoinName = 'tltc';
 
-  constructor(bitgo: BitGoBase) {
-    super(bitgo);
-    this.altScriptHash = utxolib.networks.testnet.scriptHash;
-    // support alt destinations on test
-    this.supportAltScriptDestination = false;
-  }
   static createInstance(bitgo: BitGoBase): Tltc {
     return new Tltc(bitgo);
   }