Fix bundle installation error on GitHub Action

[aYukiSekiguchi]

This commit attempts to fix the GitHub Actions failure in PR #142.

Ruby 3.2 Unit Testing on ubuntu-latest

The installation path is insecure. Bundler cannot continue.
/opt/hostedtoolcache/Ruby/3.2.5/x64/lib/ruby/gems/3.2.0/gems is world-writable (without sticky bit).
Bundler cannot safely replace gems in world-writable directories due to potential vulnerabilities.
Please change the permissions of this directory or choose a different install path.
Error: Process completed with exit code 38.

The last commit to the main branch was successful, but it was 5 months ago (Apr 30). It seems that an update to Ruby or Bundler may have broken the Action.

Based on my testing in my repository, this fix resolves the issue: PR #1.