fix(charts): update helm release loki to v6.6.4

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
loki (source)	patch	6.6.3 -> 6.6.4

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Release Notes

grafana/helm-charts (loki)

### [`v6.6.4`](https://togithub.com/grafana/helm-charts/releases/tag/grafana-6.6.4) The leading tool for querying and visualizing time series and metrics.

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