Ruby 2.4 is EOL

Author: eregon

README.md

@@ -81,7 +81,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ ubuntu-latest, macos-latest ]
-        ruby: [ 2.4, 2.5, 2.6, 2.7, jruby, truffleruby ]
+        ruby: [ 2.5, 2.6, 2.7, jruby, truffleruby ]
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2