Changed grammar for better readability

guides/source/active_support_core_extensions.md

@@ -2216,7 +2216,7 @@ NOTE: Defined in `active_support/core_ext/array/conversions.rb`.
 
 The method `to_formatted_s` acts like `to_s` by default.
 
-If the array contains items that respond to `id`, however, it may be passed the symbol `:db` as argument. That's typically used with collections of ARs. Returned strings are:
+If the array contains items that respond to `id`, however, the symbol `:db` may be passed as argument. That's typically used with collections of ActiveRecord objects. Returned strings are:
 
 ```ruby
 [].to_formatted_s(:db)            # => "null"