Update Promtail to v2.9.2 and chart to 6.15.3

This MR contains the following updates:

Package	Update	Change
ironbank/opensource/grafana/promtail	patch	v2.9.1 -> v2.9.2
registry1.dso.mil/ironbank/opensource/grafana/promtail	patch	v2.9.1 -> v2.9.2

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