Test failure in TestHnswFloatVectorGraph

### Description

./gradlew :lucene:core:test --tests "org.apache.lucene.util.hnsw.TestHnswFloatVectorGraph.testSortedAndUnsortedIndicesReturnSameResults" -Ptests.jvms=4 -Ptests.jvmargs= -Ptests.seed=7E8BF358C8C87828 -Ptests.multiplier=2 -Ptests.directory=MMapDirectory -Ptests.gui=true -Ptests.file.encoding=UTF-8 -Ptests.vectorsize=512

reproduces for me. I also tried it in 9.8.0 and it ~~still reproduces~~ does not repro (too many open terminals, git branches, I lost track of what I was doing for a moment)

Start by running the exact Gradle command in the issue for org.apache.lucene.util.hnsw.TestHnswFloatVectorGraph.testSortedAndUnsortedIndicesReturnSameResults, preserving the listed seed and options. Inspect the resulting failure and the named test to determine whether the failure is reproducible; done means the targeted test reliably passes with the regression understood and addressed.

Written by the indexing model from the issue text.