Fix FixtureSupport's run_in_transaction? method

`ActiveRecord::TestFixture`'s `uses_transaction` is designed to be used
like this:

```ruby
uses_transaction :the_test_method_name
```

And in RSpec, the method name would be the example's name.

```ruby
uses_transaction "does someting"

it "does someting" {}
```

But in the current implementation, it's passing the example object
instead of its name, which would always fail the name comparison in
https://github.com/rails/rails/blob/main/activerecord/lib/active_record/test_fixtures.rb#L94-L97

So this commit fixes the issue by passing the example's name instead of
the example object.

lib/rspec/rails/fixture_support.rb

@@ -13,7 +13,8 @@ module FixtureSupport
         # Monkey patched to avoid collisions with 'let(:name)' in Rails 6.1 and after
         # and let(:method_name) before Rails 6.1.
         def run_in_transaction?
-          use_transactional_tests && !self.class.uses_transaction?(self)
+          current_example_name = (RSpec.current_example && RSpec.current_example.metadata[:description])
+          use_transactional_tests && !self.class.uses_transaction?(current_example_name)
         end
 
         included do