Remove docs regarding grouping multiple values, as we should avoid

duplicating API reference in guides. Also ✂ [ci skip]

guides/source/active_record_querying.md

@@ -676,23 +676,6 @@ FROM "orders"
 GROUP BY status
 ```
 
-It is possible to do this count with multiple values, to do this only add the
-other column to `group`.
-
-```ruby
-Order.group(:status, :delivery_method).count
-# =>  { ['awaiting_approval', 'regular'] => 5, ['awaiting_approval', 'fast'] => 2, ['paid', 'regular'] => 2, ['paid', 'fast'] => 10 }
-```
-
-The SQL that would be executed would be something like this:
-
-```sql
-SELECT COUNT (*) AS count_all, status AS status,
-delivery_method AS delivery_method
-FROM "orders"
-GROUP BY status, delivery_method
-```
-
 Having
 ------