Update renovate/pro Docker tag to v0.18.0

Author: renovate-bot

examples/docker-compose-gitlab.yml

@@ -1,7 +1,7 @@
 version: "3.6"
 services:
   renovate:
-    image: renovate/pro:0.14.0
+    image: renovate/pro:0.18.0
     restart: on-failure
     environment:
       - ACCEPT_AGREEMENT # You must accept the Renovate User Agreement ot use the image