fix: update helm release promtail to v6.15.3

This MR contains the following updates:

Package	Update	Change
promtail (source)	patch	6.15.2 -> 6.15.3

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Release Notes

grafana/helm-charts (promtail)

v6.15.3

Compare Source

Promtail is an agent which ships the contents of local logs to a Loki instance

What's Changed

• [promtail] bump promtail version to 2.9.2 by @​emilkor1 in https://github.com/grafana/helm-charts/pull/2715

Full Changelog: https://github.com/grafana/helm-charts/compare/loki-distributed-0.76.0...promtail-6.15.3

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