Don't run specs against Ruby 2.7 because it's reached EOL

Author: andrykonchin

.github/workflows/ci.yml

@@ -215,7 +215,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['2.7', '3.0', '3.1']
+        ruby: ['3.0', '3.1']
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2