Fix uninitialized constant RSpec::Rails::OpenStruct error

This started to occur on recent test suite runs. It may be related to a json gem update that removed the ostruct dependency as I encountered this with turbo_tests and a fix for that is in serpapi/turbo_tests#49 with more details.

spec/rspec/rails/example/view_example_group_spec.rb

@@ -1,3 +1,4 @@
+require 'ostruct'
 require 'support/group_failure_formatter'
 
 module RSpec::Rails
@@ -187,7 +188,7 @@ def _default_file_to_render; end # Stub method
         Class.new do
           include ViewExampleGroup::ExampleMethods
           def controller
-            @controller ||= OpenStruct.new(params: nil)
+            @controller ||= ::OpenStruct.new(params: nil)
           end
         end.new
       end