Update Data Plane API spec server URL and variable (#14)

* Change server url values and variables to work with Bump API explorer proxy

* Fix default value

Author: kbatuigas

cloud-dataplane/cloud-dataplane.yaml

@@ -4975,14 +4975,14 @@ security:
   - auth0: []
 servers:
   - description: Data Plane API
-    url: '{dataplane_api_url}'
+    url: 'https://{dataplane_api_url}.cloud.redpanda.com'
     variables:
       dataplane_api_url:
-        default: https://{dataplane_api_url}
+        default: "dataplane_api.url"
         description: |-
           Find the Data Plane API base URL of a cluster by calling the Get Cluster endpoint of the Control Plane API. The dataplane_api.url field is returned in the response body.<br><br>
-          					Example (Dedicated): "https://api-a4cb21.ck09mi9c4vs17hng9gig.fmc.prd.cloud.redpanda.com"<br>
-          					Example (BYOC): "https://api-a4cb21.ck09mi9c4vs17hng9gig.byoc.prd.cloud.redpanda.com"
+          Example (Dedicated): "https://api-a4cb21.ck09mi9c4vs17hng9gig.fmc.prd.cloud.redpanda.com"<br>
+          Example (BYOC): "https://api-a4cb21.ck09mi9c4vs17hng9gig.byoc.prd.cloud.redpanda.com"
 tags:
   - description: Manage Redpanda access control lists (ACLs). See [Redpanda Cloud Authorization](https://docs.redpanda.com/redpanda-cloud/security/authorization/cloud-authorization/) for more information.
     name: Redpanda ACLs