ci: Update Ruby versions to match gemspec requirement

- Update minimum Ruby version from 3.0/3.1 to 3.2 in all workflows
- Remove obsolete exclude for Ruby 3.1 with Rails 8
- Ensure all CI jobs use Ruby >= 3.2 to match gemspec requirement

.github/workflows/specs_rails61.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        ruby: ['3.0']
+        ruby: ['3.2']
 
     env:
       RAILS_VERSION: 6.0