CI: Add Ruby 3.3

[olleolleolle]

This PR adds Ruby 3.3 to the build matrix and updates to the actions/checkout@4.

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ERROR:  Error installing standardrb:
	The last version of standard (>= 0) to support your Ruby & RubyGems was 1.37.0. Try installing it with `gem install standard -v 1.37.0` and then running the current command again
	standard requires Ruby version >= 3.0.0. The current ruby version is 2.7.8.225.