fix: Gemfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-RAILSHTMLSANITIZER-8454495
- https://snyk.io/vuln/SNYK-RUBY-NOKOGIRI-8453714
- https://snyk.io/vuln/SNYK-RUBY-RAILSHTMLSANITIZER-8447886
- https://snyk.io/vuln/SNYK-RUBY-RAILSHTMLSANITIZER-8448218
- https://snyk.io/vuln/SNYK-RUBY-RAILSHTMLSANITIZER-8448407
- https://snyk.io/vuln/SNYK-RUBY-RAILSHTMLSANITIZER-8448516

Gemfile

@@ -4,7 +4,7 @@ ruby '3.2.2'
 
 source 'https://rubygems.org'
 
-gem 'rails', '~> 6.1'
+gem 'rails', '~> 7.0', '>= 7.0.0'
 gem 'rails-i18n', '~> 6.0'
 
 # Databases