chore: upgrade ruby 2.2 to 2.4

Author: bethesque

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby_version: ["2.2", "2.7"]
+        ruby_version: ["2.4", "2.7"]
         experimental: [false]
         include:
           - ruby_version: "3.0"