Update dependency it.unimi.dsi:fastutil to v8.5.15

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
it.unimi.dsi:fastutil (source)	8.5.14 -> 8.5.15

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Release Notes

vigna/fastutil (it.unimi.dsi:fastutil)

### [`v8.5.15`](https://redirect.github.com/vigna/fastutil/compare/8.5.14...8.5.15) [Compare Source](https://redirect.github.com/vigna/fastutil/compare/8.5.14...8.5.15)

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Configuration

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