Fix and Re-Enable Ruby Testing on macos-latest

[bashbaug]

To unblock an upcoming release, PR https://github.com/KhronosGroup/OpenCL-SDK/pull/103 changed the GitHub runner for Ruby testing from macos-latest back to macos-13. This issue is to track fixing the CI config for Ruby on macos-latest and re-enabling testing with the latest runner.

For reference, the failure was:

Run rake test
  rake test
  shell: /bin/bash -e {0}
Warning OpenCL 1.2 loader detected!
Warning: could not find extension function clReleaseDeviceEXT!
Warning: could not find extension function clRetainDeviceEXT!
Warning: could not find extension function clCreateSubDevicesEXT!
Warning: could not find extension function clGetKernelSubGroupInfoKHR!
Warning: could not find extension function clGetGLContextInfoKHR!
/Users/runner/.local/share/gem/ruby/[3](https://github.com/KhronosGroup/OpenCL-SDK/actions/runs/8885606590/job/24397324466#step:6:3).0.0/gems/opencl_ruby_ffi-1.3.13/lib/opencl_ruby_ffi/opencl_ruby_ffi_base.rb:[4](https://github.com/KhronosGroup/OpenCL-SDK/actions/runs/8885606590/job/24397324466#step:6:5)45:in `error_check': -30 (OpenCL::Error::INVALID_VALUE)
	from /Users/runner/.local/share/gem/ruby/3.0.0/gems/opencl_ruby_ffi-1.3.13/lib/opencl_ruby_ffi/Platform.rb:116:in `devices'
	from /Users/runner/work/OpenCL-SDK/OpenCL-SDK/ruby/copybuffer/copybuffer.rb:19:in `<top (required)>'
	from <internal:/opt/homebrew/lib/ruby/site_ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:136:in `require'
	from <internal:/opt/homebrew/lib/ruby/site_ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:136:in `require'
	from /opt/homebrew/Cellar/[email protected]/3.0.6_1/lib/ruby/gems/3.0.0/gems/rake-13.0.3/lib/rake/rake_test_loader.rb:17:in `block in <main>'
	from /opt/homebrew/Cellar/[email protected]/3.0.6_1/lib/ruby/gems/3.0.0/gems/rake-13.0.3/lib/rake/rake_test_loader.rb:[5](https://github.com/KhronosGroup/OpenCL-SDK/actions/runs/8885606590/job/24397324466#step:6:6):in `select'
	from /opt/homebrew/Cellar/[email protected]/3.0.6_1/lib/ruby/gems/3.0.0/gems/rake-13.0.3/lib/rake/rake_test_loader.rb:5:in `<main>'
rake aborted!
Command failed with status (1)

Tasks: TOP => test
(See full trace by running task with --trace)