Bring back few old ruby/rails matrix to CI

Author: wasifhossain

.github/workflows/ci.yml

@@ -37,6 +37,10 @@ jobs:
             rails-version: '7.0'
           - ruby-version: '2.7'
             rails-version: '6.1'
+          - ruby-version: '2.7'
+            rails-version: '6.0'
+          - ruby-version: '2.6'
+            rails-version: '6.1'
           - ruby-version: '2.6'
             rails-version: '6.0'
           - ruby-version: '2.6'