ci: run on Ruby 3.2 instead of head

Author: G-Rath

.github/workflows/ci.yml

@@ -7,8 +7,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [2.7, '3.0', 3.1, ruby-head]
-    continue-on-error: ${{ endsWith(matrix.ruby, 'head') }}
+        ruby: [2.7, '3.0', '3.1', '3.2']
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2