[8.12] [ILM] Add missing deprecated param to API schema (#175440) (#1…

…75862)

# Backport

This will backport the following commits from `main` to `8.12`:
- [[ILM] Add missing deprecated param to API schema
(#175440)](#175440)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Ignacio
Rivas","email":"[email protected]"},"sourceCommit":{"committedDate":"2024-01-30T06:11:26Z","message":"[ILM]
Add missing deprecated param to API schema
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missing deprecated param to API
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Add missing deprecated param to API schema
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Add missing deprecated param to API schema
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BACKPORT-->

Co-authored-by: Ignacio Rivas <[email protected]>

x-pack/plugins/index_lifecycle_management/server/routes/api/policies/register_create_route.ts

@@ -33,6 +33,7 @@ async function createPolicy(
  */
 const bodySchema = schema.object({
   name: schema.string(),
+  deprecated: schema.maybe(schema.boolean()),
   phases: schema.object({
     hot: schema.any(),
     warm: schema.maybe(schema.any()),