Update getting-started-slm.asciidoc

Changed the example schedule from 1:30 to 2:30 as the default of slm.retention_schedule to delete snapshot is 1:30 as well.
If a customer just copy/paste the snippet it can end up with no snapshot being deleted.

docs/reference/slm/getting-started-slm.asciidoc

@@ -48,7 +48,7 @@ how retention works.
 --------------------------------------------------
 PUT /_slm/policy/nightly-snapshots
 {
-  "schedule": "0 30 1 * * ?", <1>
+  "schedule": "0 30 2 * * ?", <1>
   "name": "<nightly-snap-{now/d}>", <2>
   "repository": "my_repository", <3>
   "config": { <4>