Stop testing against Ruby 3.1

Author: st0012

.github/workflows/ci.yml

@@ -44,7 +44,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        ruby: ["3.1", "3.2", "3.3", "3.4"]
+        ruby: ["3.2", "3.3", "3.4"]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 30
     name: Ruby ${{ matrix.ruby }} on ${{ matrix.os }}