chore(deps): update grafana/loki docker tag to v3.6.8

Author: renovate[bot]

compose-debug.yml

@@ -31,7 +31,7 @@ services:
     restart: unless-stopped
 
   loki:
-    image: grafana/loki:${LOKI_VERSION:-3.6.7}
+    image: grafana/loki:${LOKI_VERSION:-3.6.8}
     user: ":"
     command: -config.file=/etc/loki/loki.yml
     volumes: