Decrease queue capacity in EnrichResiliencyTests for resiliency

[gmarouli]

Fixes #82719 according to the recommendation in #82719 (comment).

I think this failed in CI, because of slowness. The executes a bulk request with a number of index requests (50) and then assumes that some of these index requests failed, because enrich queue was at capacity. The queue capacity is set to 10. I think we should to set the queue size to an even smaller value, like 2. To make it likely to reach queue capacity when test execution is slow.

In the mentioned build failure, it took 12 seconds to run this test, while locally here it takes 707 ms.

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)