playground/testdata/src/ids: make Duration for 'expired' 1ns instead of 0

https://vanadium-review.googlesource.com/#/c/4903 changes the meaning of the 0
value for the principal tool's --for flag to be 'no expiration'.

MultiPart: 2/2
Change-Id: I6b4f2c15a00cbb07f288feaf3bfbd18099261839
diff --git a/go/src/playground/testdata/src/ids/expired.id b/go/src/playground/testdata/src/ids/expired.id
index 446851f..70b7121 100644
--- a/go/src/playground/testdata/src/ids/expired.id
+++ b/go/src/playground/testdata/src/ids/expired.id
@@ -6,7 +6,7 @@
 {
   "Name": "myclient",
   "Blesser": "myserver",
-  "Duration": "0s",
+  "Duration": "1ns",
   "Files": ["ping.go", "ping.js"]
 }
 ]