Define timezone as variable

ansible/roles/forrest/files/docker-compose.yml

@@ -4,7 +4,7 @@ services:
   grafana:
     image: grafana/grafana:latest
     environment:
-      - TZ=Europe/London
+      - TZ={{ TZ }}
       - GF_DATABASE_URL=postgres://grafana:grafana@db/grafana
       - GF_RENDERING_SERVER_URL=http://renderer:8081/render
       - GF_RENDERING_CALLBACK_URL=http://grafana:3000/
@@ -30,4 +30,4 @@ services:
     image: grafana/grafana-image-renderer:latest
     restart: unless-stopped
     environment:
-      - BROWSER_TZ=Europe/London
+      - BROWSER_TZ={{ TZ }}