Update docker.elastic.co/kibana/kibana Docker tag to v8.12.0

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
docker.elastic.co/kibana/kibana (source)	minor	8.11.4 -> 8.12.0

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Release Notes

elastic/kibana (docker.elastic.co/kibana/kibana)

### [`v8.12.0`](https://togithub.com/elastic/kibana/releases/tag/v8.12.0): Kibana 8.12.0 [Compare Source](https://togithub.com/elastic/kibana/compare/v8.11.4...v8.12.0) Downloads: https://elastic.co/downloads/kibana Release notes: https://www.elastic.co/guide/en/kibana/8.12/release-notes-8.12.0.html

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