Remove unused env-var - grafana

Author: mrnicegyu11

services/monitoring/grafana/template-config.monitoring

@@ -3,8 +3,6 @@ GF_SECURITY_ADMIN_USER=${SERVICES_USER}
 GF_USERS_ALLOW_SIGN_UP=false
 GF_SERVER_ROOT_URL=https://${MONITORING_DOMAIN}/grafana
 GF_INSTALL_PLUGINS=grafana-piechart-panel, grafana-worldmap-panel, grafana-polystat-panel
-# NOTE: grafana image rendering plugin: https://grafana.com/blog/2020/05/07/grafana-7.0-preview-new-image-renderer-plugin-to-replace-phantomjs/
-GF_RENDERING_SERVER_URL=http://grafana-image-renderer:8081/render
 GF_RENDERING_CALLBACK_URL=http://grafana:3000/
 GF_LOG_FILTERS=rendering:debug
 GF_SERVER_DOMAIN=${MONITORING_DOMAIN}