CI: Run ruby/spec on CRuby 3.2 too

* To ensure 3.2 specs added work fine on CRuby.

Author: eregon

.github/workflows/ci.yml

@@ -242,7 +242,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.0', '3.1']
+        ruby: ['3.0', '3.1', '3.2']
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2