Fix version check in ActiveRecord adapter

Fix version check in ActiveRecord adapter: the "target" version for comparison needs to be a string.

Fixes: 
ArgumentError: comparison of Gem::Version with 7.2 failed

lib/graphiti/adapters/active_record.rb

@@ -304,7 +304,7 @@ def destroy(model_instance)
       end
 
       def close
-        if ::ActiveRecord.version > 7.2
+        if ::ActiveRecord.version > '7.2'
           ::ActiveRecord::Base.connection_handler.clear_active_connections!
         else
           ::ActiveRecord::Base.clear_active_connections!