Relax the threshold of a flaky test

[marianotepper]

Relax the threshold of OnHeapGraphIndexTest.testIncrementalInsertionFromOnDiskIndex_withIdentityOrdinalMapping as it was flaky

[github-actions]

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[marianotepper]

I run 10k instances with this threashold on my machine and it seemed to have done the job. However, PRs are still failing because of this test:
OnHeapGraphIndexTest.testIncrementalInsertionFromOnDiskIndex_withIdentityOrdinalMapping:274 Recall mismatch, recallFromReconstructedAllNodeOnHeapGraphIndex: 0.686000 != recallFromAllGraphIndex: 0.606000 expected:<0.6859998> but was:<0.6059998>
The gap is 0.08 instead of 0.06, which is the value I used. We could change it to 0.07, but it looks like 8% recall drop is pretty significant. This to me indicates that there are deeper problems with the functionality behind this test. This is related to #568.

[marianotepper]

The functionality that this test is evaluating is not working correctly and is tagged as experimental. The test remains flaky and the level of relaxation needed to get rid of the flakiness is starting to get unacceptable. Marking the test as @Ignore until the functionality receives proper attention.

[tlwillke]

Looks good to ignore the test for now. We will decide what to do with the related contribution. We can then revisit the recall threshold or permanently remove the test and related work.