Attempt to fix minitest/mock loading on CI

Author: avsej

Gemfile

@@ -20,6 +20,7 @@ git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
 gemspec
 
 gem "rake"
+gem "minitest"
 
 group :development do
   gem "activesupport", "~> 7.0.3"
@@ -30,7 +31,6 @@ group :development do
   gem "gem-compiler"
   gem "grpc-tools", "~> 1.59"
   gem "heckle"
-  gem "minitest"
   gem "minitest-reporters"
   gem "mutex_m"
   gem "rack"