Update teslamate.md

Updated host name for postgres

docs/sandbox/apps/teslamate.md

@@ -30,7 +30,7 @@ To use a custom subdomain, add a custom value for `teslamate_web_subdomain` in t
 
 Once installation is finished, you will need to add the teslamate data source in grafana under connections.
 
-Host URL: postgres:5432 (or whatever port your postgres is running)
+Host URL: This is based upon the {{ teslamate_name }}-postgres variable. Default is teslamate-postgres:5432
 Table: teslamate
 
 Authentication for Postgres: '<https://docs.saltbox.dev/apps/postgres/?h=postgres>'