Update dependency ruby to v2.7.3

.ruby-version

@@ -1 +1 @@
-2.6.5
+2.7.3

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.6.5
+FROM ruby:2.7.3
 
 ENV LANG=C.UTF-8
 ENV ENABLE_SERVICE_WORKER=true