Lock minitest to < 6

We still need to support Rails 7.1.

Author: rafaelfranca

Gemfile

@@ -13,3 +13,5 @@ elsif ENV["RAILS_VERSION"]
 else
   gem "activesupport"
 end
+
+gem "minitest", "< 6"

test/support/application_generator.rb

@@ -53,6 +53,7 @@ def generate_files
         FileUtils.rm_rf(application.path("test/performance"))
 
         append_to_file(application.gemfile, "gem 'spring', '#{Spring::VERSION}'")
+        append_to_file(application.gemfile, "gem 'minitest', '< 6'")
 
         append_to_file(application.path("config/boot.rb"), "raise 'BOOM' if ENV['CRASH_ON_BOOT']")