Load spec helper not knowing Rails

When the application is not preloaded then running Rspec doesn't know
Rails until the spec helper is loaded. So we can't use Rails to find the
path of the spec helper. This has been fixed before but the DFC Address
code was developed at the same time and missed.

engines/dfc_provider/spec/requests/addresses_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/swagger_helper")
+require_relative "../swagger_helper"
 
 describe "Addresses", type: :request, swagger_doc: "dfc.yaml", rswag_autodoc: true do
   let(:user) { create(:oidc_user) }

engines/dfc_provider/spec/services/address_builder_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe AddressBuilder do
   subject(:result) { described_class.address(address) }