Update skip versions for flat_object tests

[msfroh]

Description

While fixing a flat_object bug, I noticed that we were skipping all related yamlRestTests on pre-3.0 versions. Since the flat object field type was added in 2.7, that should be the correct skip level for most tests. The bug I fixed is still present in 2.16 and earlier, so the test that covers that fix needs to be skipped pre-2.17.

Related Issues

https://github.com/opensearch-project/OpenSearch/pull/15431

Check List

• [x] Functionality includes testing.
• [ ] API changes companion pull request created, if applicable.
• [ ] Public documentation issue/PR created, if applicable.

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[github-actions[bot]]

:x: Gradle check result for 60ee8dae33a190d342b3016cd3e75b27c7f29293: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions[bot]]

:x: Gradle check result for 60ee8dae33a190d342b3016cd3e75b27c7f29293: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions[bot]]

:x: Gradle check result for 60ee8dae33a190d342b3016cd3e75b27c7f29293: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions[bot]]

:white_check_mark: Gradle check result for 60ee8dae33a190d342b3016cd3e75b27c7f29293: SUCCESS

[dblock]

@msfroh care to contribute some flat_object examples/schema/tests to https://github.com/opensearch-project/opensearch-api-specification?