Bump minimum Ruby to 3.2

[p-linnane]

Same as #914. Ruby 3.1 was EOL 9 months ago.

Could not find compatible versions

Because minitest >= 6.0.0.a1 depends on Ruby >= 3.2
  and Gemfile depends on minitest = 6.0.0,
  Ruby >= 3.2 is required.
So, because current Ruby version is = 3.1.6,
  version solving has failed.

Not adding Ruby 4.0 to the test matrix yet.

[Copilot]

Pull request overview

This PR bumps the minimum required Ruby version from 3.1 to 3.2, reflecting that Ruby 3.1 reached end-of-life 9 months ago. The change is motivated by minitest 6.0.0 requiring Ruby >= 3.2.

• Updated minimum Ruby version requirement to 3.2 across all configuration files
• Removed Ruby 3.1 from the CI test matrix
• Maintained testing for Ruby 3.2, 3.3, and 3.4

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
ruby-macho.gemspec	Updated required_ruby_version from >= 3.1 to >= 3.2
.rubocop.yml	Updated TargetRubyVersion from 3.1 to 3.2
.github/workflows/tests.yml	Removed Ruby 3.1 from the test matrix, keeping 3.2, 3.3, and 3.4

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[woodruffw]

/me shakes fist at github

[woodruffw]

I no longer have permission to edit the workflow settings on this repo, so someone else will need to 😅 -- @p-linnane I bet you probably have access! I think we can just remove these matrix entries.

[p-linnane]

@woodruffw I fixed your permissions so you should be good moving forward.