No longer test for Ruby 3.0 or 3.1

.github/workflows/continuous-integration.yml

@@ -6,18 +6,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ["3.0", "3.1", "3.2", "3.3"]
+        ruby: ["3.2", "3.3"]
         db: [sqlite, mysql, postgres]
-        exclude:
-          - ruby: "3.1"
-            db: sqlite
-          - ruby: "3.1"
-            db: postgres
-          - ruby: "3.2"
-            db: sqlite
-          - ruby: "3.2"
-            db: postgres
-
     steps:
       - uses: actions/checkout@v1
       - run: bash -x script/cibuild ${{ matrix.ruby }} ${{ matrix.db }}