promtail update to 6.15.5-bb.7

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/promtail/-/blob/6.15.5-bb.7/CHANGELOG.md

Package MR

big-bang/product/packages/promtail!83 (merged)

For Issue

Closes big-bang/product/packages/promtail#52 (closed)

Upgrade Notices

This upgrade changes the default labels that will be appended to logs shipped to Loki. This will not affect your existing logs or the data within these logs, however, logs going forward will only be given these set labels according to Loki best practices.