WIP: chore: required rubocop linting for ruby-head

[Hunga1]

Re-enables rubocop linting for ruby-head (3.1.0) during the test and deploy GitHub Action.

Changes include:

• Upgraded rubocop to the latest version (1.24.1) to support linting of Ruby 3.1.0 (>= v1.22.3)
• Updated rubocop.yml target ruby version from 2.4 to 2.5 (support for Ruby 2.4 dropped after v1.12)
• Removed liniting step from make test. Command now just executes unit tests.
• Added a linting step to the GitHub Action test job that excludes rubocop's unsupported ruby versions

Checklist

• [x] I acknowledge that all my contributions will be made under the project's license
• [ ] I have made a material change to the repo (functionality, testing, spelling, grammar)
• [ ] I have read the Contribution Guidelines and my PR follows them
• [ ] I have titled the PR appropriately
• [ ] I have updated my branch with the main branch
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added the necessary documentation about the functionality in the appropriate .md file
• [ ] I have added inline documentation to the code I modified

If you have questions, please file a support ticket, or create a GitHub Issue in this repository.

[Hunga1]

Closing this PR to take a different approach.