Adds a required type tag to the open API spec of Logstash APIs. (#18169)

* Add required for the queue.type of PipelineQueueStats in openapi spec definition.

Author: mashhurs

docs/static/spec/openapi/logstash-api.yaml

@@ -2296,6 +2296,8 @@ components:
           oneOf:
             - type: object
               description: "The metrics of persisted queue."
+              required:
+                - type
               properties:
                 type:
                   type: string
@@ -2340,6 +2342,8 @@ components:
                   format: int64
             - type: object
               description: "The metrics of memory queue."
+              required:
+                - type
               properties:
                 type:
                   type: string