[rails] Use Ruby 3.4-rc (#9087)

frameworks/Ruby/rails/rails-mysql.dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:3.3
+FROM ruby:3.4-rc
 
 RUN apt-get update -yqq && apt-get install -yqq --no-install-recommends redis-server
 

frameworks/Ruby/rails/rails.dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:3.3
+FROM ruby:3.4-rc
 
 RUN apt-get update -yqq && apt-get install -yqq --no-install-recommends redis-server