Upgraded Teleport to version 15.3.7

We’ve upgraded all Teleport clusters to 15.3.7. Teleport is a tool we mostly use internally to provide secure and auditted access to (EC2) instances, Kubernetes clusters and several dashboards. The nodes will gradually be upgraded to the new version when new instances are launched. You can find more information on this release in the Teleport changelog. In particular, several high-level security fixes were done in 15.3.6