🤖 Favor Rails.root to ensure correct path

In CI we're seeing this error:

```
LoadError:
  cannot load such file -- /app/samvera/spec/hyrax-webapp/config/environment
```

The rails_helper is in the /app/samvera/spec directory and then it's
trying to load the environment from the hyrax-webapp directory within
its current directory.

spec/rails_helper.rb

@@ -5,14 +5,17 @@
 
 ENV["RAILS_ENV"] ||= "test"
 # require File.expand_path('../config/environment', __dir__)
-require File.expand_path("hyrax-webapp/config/environment", __dir__)
+require Rails.root.join("config", "environment")
 # Prevent database truncation if the environment is production
 abort("The Rails environment is running in production mode!") if Rails.env.production?
 require "rspec/rails"
 # Add additional requires below this line. Rails is not loaded until this point!
 require "factory_bot_rails"
-FactoryBot.definition_file_paths = [File.expand_path("spec/factories", HykuAddons::Engine.root)]
-FactoryBot.find_definitions
+
+if defined?(HykuAddons)
+  FactoryBot.definition_file_paths = [File.expand_path("spec/factories", HykuAddons::Engine.root)]
+  FactoryBot.find_definitions
+end
 
 # Requires supporting ruby files with custom matchers and macros, etc, in
 # spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are