Drop Ruby 2.3 CI

It continually segfaults when trying to create an OpenSSL cipher.

Author: jeremyevans

.github/workflows/ci.yml

@@ -25,7 +25,6 @@ jobs:
         ruby: [ "2.0.0", 2.1, 2.4, 2.5, 2.6, 2.7, "3.0", 3.1, 3.2, 3.3, 3.4 ]
         include:
           - { os: ubuntu-22.04, ruby: "1.9.3" }
-          - { os: ubuntu-22.04, ruby: 2.3 }
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.ruby }}
     env: