Update varnish

docker/services/varnish

@@ -1,4 +1,3 @@
-    network_mode: 'service:tinc'
     image: varnish:7.3-alpine
     command: "-p default_keep=300"
     ports:
@@ -14,3 +13,5 @@
     depends_on:
       - tinc
     restart: always
+    networks:
+      - ${netname}_internal