Test on 2.7 - 3.3. Drop TruffleRuby

Add 3.2 and 3.3 to testing matrix. Drop truffleruby until such time as a user mentions it, as it sometimes fails and there’s no evidence it is being used.

.github/workflows/main.yml

@@ -14,7 +14,7 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
-        ruby: [jruby, truffleruby, 2.5, 2.6, 2.7, '3.0', 3.1, head]
+        ruby: [jruby, 2.7, '3.0', 3.1, 3.2, 3.3, head]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/[email protected]