Update dockerfiles

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.6.3
+FROM ruby:2.6.5
 
 ENV LANG=C.UTF-8
 ENV ENABLE_SERVICE_WORKER=true

Dockerfile-alpine

@@ -1,4 +1,4 @@
-FROM ruby:2.6.3-alpine
+FROM ruby:2.6.5-alpine
 
 ENV LANG=C.UTF-8
 ENV ENABLE_SERVICE_WORKER=true