Update dependency i18next to v21.8.15

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
i18next (source)	21.8.14 -> 21.8.15

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Release Notes

i18next/i18next

### [`v21.8.15`](https://togithub.com/i18next/i18next/blob/HEAD/CHANGELOG.md#​21815) [Compare Source](https://togithub.com/i18next/i18next/compare/v21.8.14...v21.8.15) - fix: make sure retry logic ends for failed backend reads

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