[BUG] Integration tests w/ OpenSearch 2.19

[dblock]

What is the bug?

Integration tests against OpenSearch 2.19 are failing.

How can one reproduce the bug?

Change OPENSEARCH_VERSION to 2.19.0 in .github/workflows/test-integration.yml

What is the expected behavior?

Tests to pass.

What is your host/environment?

Docker.

Do you have any additional context?

Not sure what changed in 2.19 to cause node stats to not be empty, don't know if it's expected.

=== RUN   TestNodes/Stats/without_request
    api_nodes_test.go:182: 
        	Error Trace:	/Users/dblock/source/opensearch-project/opensearch-go/dblock-opensearch-go/internal/test/helper.go:147
        	            				/Users/dblock/source/opensearch-project/opensearch-go/dblock-opensearch-go/opensearchapi/api_nodes_test.go:182
        	Error:      	Should be empty, but was [{"op":"remove","path":"/nodes/WNsh2OanQ0up1zZbZsHq7w/indices/get/getTime"}]
        	Test:       	TestNodes/Stats/without_request
{"op":"remove","path":"/nodes/WNsh2OanQ0up1zZbZsHq7w/indices/get/getTime"}

Integ tests were locked to 2.18 in #667.