Fix required link issue (MystenLabs#15694)

## Description 

Describe the changes or additions included in this PR.

## Test Plan 

How did you test the new or updated feature?

---
If your changes are not user-facing and do not break anything, you can
skip the following section. Otherwise, please briefly describe what has
changed under the Release Notes section.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

.changeset/flat-zebras-agree.md

@@ -0,0 +1,5 @@
+---
+'@mysten/zksend': patch
+---
+
+Fix required redirect

sdk/zksend/src/links.ts

@@ -28,7 +28,7 @@ export interface ZkSendLinkBuilderOptions {
 	keypair?: Keypair;
 	client?: SuiClient;
 	sender: string;
-	redirect: ZkSendLinkRedirect;
+	redirect?: ZkSendLinkRedirect;
 }
 
 export interface ZkSendLinkOptions {