remove vpc peering between default subnet in gitlab-analysis project and gprd and gstg

this is a follow up on work done in this issue: https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/5970#note_177219000

The reason VPC peering was setup between gprd, gstg and gitlab-analysis was to allow the bizops GKE cluster to access db replicas. gitlab-analysis project has a default subnet that contains a number of ip ranges that are not being used. They will clash in the future causing us problems. bizops cluster will soon be deprecated at which point there will no longer be a need to have the peerings with default subnet in gitlab-analysis.

This issue is about removing those peerings

@tlapiana fyi