(#9302) Add Ruby 3.3 to CI matrix

Author: bastelfreak

.github/workflows/rspec_tests.yaml

@@ -19,6 +19,7 @@ jobs:
           - {os: ubuntu-latest, ruby: '3.1'}
           - {os: ubuntu-20.04, ruby: '3.2'} # openssl 1.1.1
           - {os: ubuntu-22.04, ruby: '3.2'} # openssl 3
+          - {os: ubuntu-22.04, ruby: '3.3'} # openssl 3 / latest Ruby
           - {os: ubuntu-latest, ruby: 'jruby-9.4.3.0'}
           - {os: windows-2019, ruby: '3.1'}
           - {os: windows-2019, ruby: '3.2'} # openssl 3