fix: Gemfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-ACTIONMAILER-8220269
- https://snyk.io/vuln/SNYK-RUBY-ACTIONPACK-8220162
- https://snyk.io/vuln/SNYK-RUBY-ACTIONPACK-8220268
- https://snyk.io/vuln/SNYK-RUBY-ACTIONTEXT-8220270

Gemfile

@@ -6,7 +6,7 @@ git_source(:github) do |repo_name|
   "https://github.com/#{repo_name}.git"
 end
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
-gem 'rails', '~> 6.1', '>= 6.1.7.8'
+gem 'rails', '~> 7.0', '>= 7.0.0'
 # Use sqlite3 as the database for Active Record
 # gem 'sqlite3', '~> 1.3'
 # Use postgres as the database for Active Record