fix: Gemfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-ACTIONPACK-6274386
- https://snyk.io/vuln/SNYK-RUBY-ACTIONPACK-6274388
- https://snyk.io/vuln/SNYK-RUBY-RACK-6274383
- https://snyk.io/vuln/SNYK-RUBY-RACK-6274384
- https://snyk.io/vuln/SNYK-RUBY-RACK-6274385

Gemfile

@@ -8,22 +8,22 @@ group :development, :test do
   gem "rake"
   gem "pry"
   gem "pry-rails"
-  gem "test-unit-rails"
+  gem "test-unit-rails", ">= 6.0.0"
   gem "test-unit-notify"
 end
 
 group :development do
   gem 'listen', '>= 3.0.5', '< 3.2'
-  gem 'i18n_generators', '2.1.1'
-  gem 'better_errors'
-  gem 'web-console', '~> 3.6'
+  gem 'i18n_generators', '2.2.0'
+  gem 'better_errors', '>= 2.5.1'
+  gem 'web-console', '~> 4.0', '>= 4.0.0'
   gem 'binding_of_caller'
 end
 
 group :test do
-  gem "factory_bot_rails"
-  gem "capybara", "~> 3.4.2"
-  gem "capybara-screenshot"
+  gem "factory_bot_rails", ">= 5.0.0"
+  gem "capybara", "~> 3.5.0"
+  gem "capybara-screenshot", ">= 1.0.23"
   gem "webdrivers"
   gem "simplecov", "~> 0.16.1", require: false
   gem "webmock", "~> 3.12.2"