ci: Separate ci matrix for the faster build

Author: toshimaru

.github/workflows/ci.yml

@@ -54,7 +54,11 @@ jobs:
       matrix:
         include:
           - ruby-version: "2.7"
-            build-rails-versions: "5.2,6.0,6.1,7.0"
+            build-rails-versions: "5.2"
+          - ruby-version: "2.7"
+            build-rails-versions: "6.0,6.1"
+          - ruby-version: "2.7"
+            build-rails-versions: "7.0"
           - ruby-version: "3.3"
             build-rails-versions: "7.1,7.2"
     steps: