Exclude ubuntu-22.04 / ruby 2.2 from CI

This avoids the following error:
     Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2
     /opt/hostedtoolcache/Ruby/2.2.10/x64/bin/gem install bundler -v ~> 1.0
     ERROR:  While executing gem ... (RuntimeError)
         Marshal.load reentered at marshal_load

See ruby/setup-ruby#496

This works fine on ubuntu 20.04 and 24.04.

.github/workflows/workflow.yml

@@ -32,6 +32,18 @@ jobs:
           - { os: macos-latest, ruby: "2.3" }
           - { os: macos-latest, ruby: "2.4" }
           - { os: macos-latest, ruby: "2.5" }
+
+          # Avoids the following error:
+          #      Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2
+          #      /opt/hostedtoolcache/Ruby/2.2.10/x64/bin/gem install bundler -v ~> 1.0
+          #      ERROR:  While executing gem ... (RuntimeError)
+          #          Marshal.load reentered at marshal_load
+          #
+          # See https://github.com/ruby/setup-ruby/issues/496
+          #
+          # This works fine on ubuntu 20.04 and 24.04.
+          - { os: ubuntu-22.04, ruby: '2.2' }
+
     steps:
       - name: repo checkout
         uses: actions/checkout@v4