Drop support for ruby 3.1

[olbrich]

This pull request updates the project's Ruby and Java versions, modernizes CI workflows, and removes legacy security and coverage integrations. The most significant changes are version upgrades for Ruby and Java, updates to GitHub Actions for testing, and the removal of the CodeQL analysis workflow.

Version upgrades:

• Updated Ruby version from 3.1.6 to 3.2.9 in .ruby-version and .tool-versions to ensure the project uses a more recent Ruby release. [1] [2]
• Updated Java version from adoptopenjdk-18.0.1+10 to adoptopenjdk-jre-21.0.9+10.0.LTS in .tool-versions for compatibility and security improvements.

CI workflow improvements:

• Updated the Ruby matrix in .github/workflows/tests.yml to drop Ruby 3.1 and add support for jruby-10.0, reflecting current supported runtimes.
• Updated actions/checkout in CI workflows to use version v6.0.1 for better reliability and security.

Removal of legacy integrations:

• Removed the entire CodeQL analysis workflow by deleting .github/workflows/codeql-analysis.yml, relying on default configurations for automated code scanning for vulnerabilities.
• Commented out the CodeClimate coverage integration in .github/workflows/tests.yml with a note that the integration is currently broken due to upstream changes.

Other minor changes:

• Updated copyright year in lib/ruby_units/unit.rb.
• Fixed table formatting in README.md for better readability.