CI: Fix core_assertions LoadError in Windows cases

[junaruga]

I faced the following test failures in Windows cases in my fork repository. Let me test it in this repository.

https://github.com/junaruga/ruby-drb/actions/runs/32027865148/job/95381019434

Run bundle exec rake
D:/a/ruby-drb/ruby-drb/test/lib/helper.rb:2:in 'Kernel#require': cannot load such file -- core_assertions (LoadError)
from D:/a/ruby-drb/ruby-drb/test/lib/helper.rb:2:in '<top (required)>'
from <internal:D:/rubyinstaller-head-x64/lib/ruby/4.1.0+4/rubygems/core_ext/kernel_require.rb>:139:in 'Kernel#require'
rake aborted!
Command failed with status (1)
D:/a/ruby-drb/ruby-drb/vendor/bundle/ruby/4.1.0+4/gems/rake-13.4.2/exe/rake:27:in '<top (required)>'
D:/rubyinstaller-head-x64/bin/bundle:33:in '<main>'
Tasks: TOP => default => test
(See full trace by running task with --trace)
Error: Process completed with exit code 1.

[junaruga]

OK. The CI failure was reproduced below.

https://github.com/ruby/drb/actions/runs/32029577375/job/95386338154?pr=54

[junaruga]

I use this PR to fix the CI failures. I rebased the PR.

The updated commit message is below.

---

This commit fixes the following CI failures in Windows.
I don't know why this change fixed. Perhaps Bundler's handling with git
repository is different.

https://github.com/ruby/drb/actions/runs/32029577375/job/95386338154?pr=54

D:/a/drb/drb/test/lib/helper.rb:2:in 'Kernel#require': cannot load such file -- core_assertions (LoadError)
from D:/a/drb/drb/test/lib/helper.rb:2:in '<top (required)>'
from <internal:D:/rubyinstaller-head-x64/lib/ruby/4.1.0+4/rubygems/core_ext/kernel_require.rb>:139:in 'Kernel#require'
rake aborted!
Command failed with status (1)
D:/a/drb/drb/vendor/bundle/ruby/4.1.0+4/gems/rake-13.4.2/exe/rake:27:in '<top (required)>'
D:/rubyinstaller-head-x64/bin/bundle:33:in '<main>'
Tasks: TOP => default => test
(See full trace by running task with --trace)
Error: Process completed with exit code 1.

[junaruga]

@hsbt Could you review this PR? Perhaps the CI failures may come from Bundler's issue.

[kou]

Could you open a new issue at https://github.com/ruby/rubygems instead of using this repository for this problem?

[junaruga]

I meant this PR was just to fix the CI as a workaround. Nothing more than that. If I want to discuss the topic related to rubygems, I will open an issue ticket on rubygems.

@kou If you don't like my PR, it's okay for you to fix the current CI failure by yourself, and close this PR.

[junaruga]

@kou Are you aware the current ruby/drb master branch has CI failures in window cases? The problem is happening in this repository. This PR is to pass the CI. That's why I used this repository.

[junaruga]

If I want to discuss the topic related to rubygems, I will open an issue ticket on rubygems.

I opend the issue ticket ruby/rubygems#9782 for bundler, let's discuss there if we have something.

[kou]

Thanks.

We can remove git: because we use only features in released test-unit-ruby-core. But let's keep this until the Bundler problem is fixed. Let's merge this after we confirm new Bundler fixes the problem in our CI.