CI: Add Ruby 3.4, Drop EOL versions (#94)

Signed-off-by: Kentaro Hayashi <[email protected]>

Author: kenhys

.github/workflows/test.yml

@@ -11,7 +11,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ['ubuntu-latest']
-        ruby: [ '3.3', '3.2', '3.1', '3.0', '2.7' ]
+        ruby: [ '3.4', '3.3', '3.2', '3.1' ]
 
     name: Ruby ${{ matrix.ruby }} on ${{ matrix.os }}
     steps: