chore(deps): update docker.elastic.co/elasticsearch/elasticsearch docker tag to v7.17.8

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
docker.elastic.co/elasticsearch/elasticsearch	patch	7.17.7 -> 7.17.8

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Release Notes

elastic/elasticsearch

### [`v7.17.8`](https://togithub.com/elastic/elasticsearch/releases/tag/v7.17.8): Elasticsearch 7.17.8 [Compare Source](https://togithub.com/elastic/elasticsearch/compare/v7.17.7...v7.17.8) Downloads: https://elastic.co/downloads/elasticsearch Release notes: https://www.elastic.co/guide/en/elasticsearch/reference/7.17/release-notes-7.17.8.html

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