No difference between JRuby and CRuby at test_read_attributes_before_type_cast_on_a_boolean

https://github.com/jruby/activerecord-jdbc-adapter ActiveRecord JDBC Adapter is actively developed
and it supports Rails 5.1 now. This pull request addresses one of the failure when running
ActiveRecord unit tests with ActiveRecord JDBC Adapter.

As of right now, ActiveRecord JDBC Adapter supports Rails 5.1, not master branch
then this test only can run on `5-1-stable` branch. But I have opened this pull request to `master` branch
since this type cast should be going to work in the future versions of ActiveRecord JDBC Adapter .

```ruby
$ ARCONN=jdbcmysql bin/test test/cases/attribute_methods_test.rb:203
Using jdbcmysql
Run options: --seed 8874

F

Finished in 0.709120s, 1.4102 runs/s, 1.4102 assertions/s.

  1) Failure:
AttributeMethodsTest#test_read_attributes_before_type_cast_on_a_boolean [/home/yahonda/git/rails/activerecord/test/cases/attribute_methods_test.rb:203]:
Expected: "0"
  Actual: 0

1 runs, 1 assertions, 1 failures, 0 errors, 0 skips
$
```

1 files changed, 1 insertions, 6 deletions

diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 2f42684212..c48f7d3518 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -200,12 +200,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   if current_adapter?(:Mysql2Adapter)
     test "read attributes_before_type_cast on a boolean" do
       bool = Boolean.create!("value" => false)
-      if RUBY_PLATFORM.include?("java")
-        # JRuby will return the value before typecast as string.
-        assert_equal "0", bool.reload.attributes_before_type_cast["value"]
-      else
-        assert_equal 0, bool.reload.attributes_before_type_cast["value"]
-      end
+      assert_equal 0, bool.reload.attributes_before_type_cast["value"]
     end
   end