Remove test-queue to reduce time taken to run tests

[tejasbubane]

For a small repository, queue is an overhead. Running minitest tests directly are much more performant.

On my machine: time bundle exec rake test
test-queue takes 16.44s
direct minitest takes 1.50s.

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Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[andyw8]

There are a couple of remaining references to test-queue:

• .github/workflows/test.yml
• Rakefile (the "JRuby and Windows..." branch can be removed)

[koic]

@tejasbubane ping.

[tejasbubane]

Thanks. Removed both references. cc @koic