Update dependency puma to v6

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

Gemfile

@@ -10,7 +10,7 @@ gem 'rails', '~> 6.0.2', '>= 6.0.2.2'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 4.3'
+gem 'puma', '~> 6.0'
 # Use SCSS for stylesheets
 gem 'sass-rails', '>= 6'
 # Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker