Remove superflous check

We don't need this check, we just need the `id.first.is_a?(Array)`
check.

Author: eileencodes

activerecord/lib/active_record/persistence.rb

@@ -527,7 +527,7 @@ def composite_query_constraints_list # :nodoc:
       #   Todo.destroy(todos)
       def destroy(id)
         multiple_ids = if composite_primary_key?
-          id.is_a?(Array) && id.first.is_a?(Array)
+          id.first.is_a?(Array)
         else
           id.is_a?(Array)
         end