Add Ruby 3.3 to CI for Ubuntu

[kojix2]

No description provided.

[kojix2]

The test fails for Ruby 2.3 and Ruby 2.4. The reason is that ffi requires Ruby 2.5 or higher.

ERROR:  Error installing pkg/iruby-0.7.4.gem:
	ffi requires Ruby version >= 2.5.
Successfully installed native-package-installer-1.1.9
Successfully installed multi_json-1.15.0
Successfully installed mime-types-data-3.2023.1205
Successfully installed mime-types-3.5.1
Error: Process completed with exit code 1.

Should iRuby also drop Ruby 2.4?

[kojix2]

It is not good that we can't test 3.3 while we don't decide whether to drop 2.3 and 2.4, so I will merge it.