Drop 2.3, 2.4, and 2.5 from test build

These version of Ruby have reached EOL.

Author: 0x1eef

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby_version: ["2.3", "2.4", "2.5", "2.6", "2.7", "3.0", "3.1", "3.2"]
+        ruby_version: ["2.6", "2.7", "3.0", "3.1", "3.2"]
         experimental: [false]
         include:
           - ruby_version: "ruby-head"