Update graylog to v6.3

Author: mend-for-github-com[bot]

Repo-Integration/Self-Managed/docker-compose.yaml

@@ -77,7 +77,7 @@ services:
     restart: "on-failure"
 
   datanode:
-    image: "graylog/graylog-datanode:6.1"
+    image: "graylog/graylog-datanode:6.3"
     hostname: "datanode-1"
     env_file:
       - .env
@@ -99,7 +99,7 @@ services:
       - "mongodb"
 
   graylog:
-    image: "graylog/graylog:6.1"
+    image: "graylog/graylog:6.3"
     hostname: "graylog-server"
     depends_on:
       mongodb: