rabbit_prometheus_http_SUITE: Use another Erlang metric

[Why]
It looks like `erlang_vm_dist_node_queue_size_bytes` is not always
present, even though other Erlang-specific metrics are present.

[How]
The goal is to ensure Erlang metrics are present in the output, so just
use another one that is likely to be there.

Author: dumbbell

deps/rabbitmq_prometheus/test/rabbit_prometheus_http_SUITE.erl

@@ -473,7 +473,7 @@ identity_info_test(Config) ->
 
 specific_erlang_metrics_present_test(Config) ->
     {_Headers, Body} = http_get_with_pal(Config, [], 200),
-    ?assertEqual(match, re:run(Body, "^erlang_vm_dist_node_queue_size_bytes{", [{capture, none}, multiline])).
+    ?assertEqual(match, re:run(Body, "^erlang_vm_dirty_io_schedulers ", [{capture, none}, multiline])).
 
 global_metrics_present_test(Config) ->
     {_Headers, Body} = http_get_with_pal(Config, [], 200),