Revert "Ensure HasManyThroughAssociation#destroy delete orphan records"

This reverts commit 7a85927.

There's still some debate about the intended behaviour in the ticket, leaving in master but removing prior to shipping 2.3.3

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -22,13 +22,6 @@ def create(attrs = nil)
         end
       end
 
-      def destroy(*records)
-        transaction do
-          delete_records(flatten_deeper(records))
-          super
-        end
-      end
-
       # Returns the size of the collection by executing a SELECT COUNT(*) query if the collection hasn't been loaded and
       # calling collection.size if it has. If it's more likely than not that the collection does have a size larger than zero,
       # and you need to fetch that collection afterwards, it'll take one fewer SELECT query if you use #length.

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -93,7 +93,7 @@ def test_delete_association
   end
 
   def test_destroy_association
-    assert_difference ["Person.count", "Reader.count"], -1 do
+    assert_difference "Person.count", -1 do
       posts(:welcome).people.destroy(people(:michael))
     end
 
@@ -102,20 +102,14 @@ def test_destroy_association
   end
 
   def test_destroy_all
-    assert_difference ["Person.count", "Reader.count"], -1 do
+    assert_difference "Person.count", -1 do
       posts(:welcome).people.destroy_all
     end
 
     assert posts(:welcome).reload.people.empty?
     assert posts(:welcome).people(true).empty?
   end
 
-  def test_should_raise_exception_for_destroying_mismatching_records
-    assert_no_difference ["Person.count", "Reader.count"] do
-      assert_raise(ActiveRecord::AssociationTypeMismatch) { posts(:welcome).people.destroy(posts(:thinking)) }
-    end
-  end
-
   def test_replace_association
     assert_queries(4){posts(:welcome);people(:david);people(:michael); posts(:welcome).people(true)}