docs: fix wait.for() idempotency example to use a single options object

wait.for() takes a single WaitForOptions object (WaitPeriod &
CommonWaitOptions), so idempotencyKey/idempotencyKeyTTL must go in the
same object as the duration. The example passed them as a second
argument, which is silently ignored — the idempotency key never applies.
This matches the wait.until() example and the section's own prose. No
behavior change.

Author: crubn

docs/wait-for.mdx

@@ -38,5 +38,5 @@ You can pass an idempotency key to any wait function, allowing you to skip waits
 
 ```ts
 // Specify the idempotency key and TTL when waiting for a duration:
-await wait.for({ seconds: 10 }, { idempotencyKey: "my-idempotency-key", idempotencyKeyTTL: "1h" });
+await wait.for({ seconds: 10, idempotencyKey: "my-idempotency-key", idempotencyKeyTTL: "1h" });
 ```