Mark 'keep_alive' for 'open_point_in_time' API as required

Co-authored-by: Seth Michael Larson <[email protected]>

Author: github-actions[bot]

output/schema/schema.json

@@ -31,6 +31,6 @@ export interface Request extends RequestBase {
     index: Indices
   }
   query_parameters: {
-    keep_alive?: Time
+    keep_alive: Time
   }
 }