[CI] Increase retry delay for Serverless tests

Author: picandocodigo

elasticsearch-api/spec/yaml-test-runner/run.rb

@@ -64,7 +64,7 @@ def serverless?
     {
       retry_on_status: [409, 400, 503],
       retry_on_failure: 10,
-      delay_on_retry: 5_000,
+      delay_on_retry: 10_000,
       request_timeout: 120
     }
   )