loki update to 6.18.0-bb.1

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/loki/-/blob/6.18.0-bb.1/CHANGELOG.md

Package MR

big-bang/product/packages/loki!287 (merged)

For Issue

Closes big-bang/product/packages/loki#211 (closed)

Upgrade Notices

Any users that were using the Loki API VirtualService (loki.<yourdomain>) without explicitly enabling it will now need to set loki.values.istio.loki.enabled to true when upgrading/installing BigBang.