Merge pull request #600 from ruby/skip-failing-test

Skip failing test with truffleruby and ubuntu-22.04

Author: hsbt

.github/workflows/test.yml

@@ -25,6 +25,7 @@ jobs:
           - { os: windows-latest, ruby: truffleruby }
           - { os: windows-latest, ruby: truffleruby-head }
           - { os: macos-latest,   ruby: truffleruby }
+          - { os: ubuntu-20.04,   ruby: truffleruby }
         include:
           - { os: windows-latest, ruby: ucrt }
           - { os: windows-latest, ruby: mswin }