Allow test_ignored_columns_not_included_in_SELECT column names case

insensitive

i.e. Oracle database identifier is UPPERCASE unlike other databases.

```ruby
(byebug) query = Developer.all.to_sql
"SELECT \"DEVELOPERS\".\"ID\", \"DEVELOPERS\".\"NAME\", \"DEVELOPERS\".\"SALARY\", \"DEVELOPERS\".\"FIRM_ID\", \"DEVELOPERS\".\"MENTOR_ID\", \"DEVELOPERS\".\"CREATED_AT\", \"DEVELOPERS\".\"UPDATED_AT\", \"DEVELOPERS\".\"CREATED_ON\", \"DEVELOPERS\".\"UPDATED_ON\" FROM \"DEVELOPERS\""
```

activerecord/test/cases/base_test.rb

@@ -1489,7 +1489,7 @@ def test_default_values_are_deeply_dupped
   end
 
   test "ignored columns not included in SELECT" do
-    query = Developer.all.to_sql
+    query = Developer.all.to_sql.downcase
 
     # ignored column
     refute query.include?("first_name")