promtail update to 6.15.0-bb.1

Package Merge Request

Package Changes

[6.15.0-bb.1] 2023-09-27

• Updated ironbank/opensource/grafana/promtail v2.8.4 -> v2.9.1
• Updated registry1.dso.mil/ironbank/opensource/grafana/promtail v2.8.4 -> v2.9.1

Package MR

big-bang/product/packages/promtail!39 (merged)

For Issue

Closes big-bang/product/packages/promtail#23 (closed)