Merge pull request #1541 from coderdojo-japan/update-rails-61

update rails 6.1

Author: nanophate

Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 ruby '3.0.6'
 
-gem 'rails', '~> 6.0'
+gem 'rails', '~> 6.1'
 gem 'puma'
 gem "puma_worker_killer"
 gem 'pg'