Refactor project import service spec to stub provider without details

It seems that the stubbed provider variable is not used to verify import
behaviour, so let's not stub it with too many details.

Note that this was caught because we've passed a Hash with String keys
to `ActiveSupport::InheritableOptions` whereas Symbol keys are expected.

spec/services/projects/import_service_spec.rb

@@ -199,12 +199,13 @@ RSpec.describe Projects::ImportService do
 
     context 'with valid importer' do
       before do
-        stub_github_omniauth_provider
+        provider = double(:provider).as_null_object
+        stub_omniauth_setting(providers: [provider])
 
         project.import_url = 'https://github.com/vim/vim.git'
         project.import_type = 'github'
 
-        allow(project).to receive(:import_data).and_return(double.as_null_object)
+        allow(project).to receive(:import_data).and_return(double(:import_data).as_null_object)
       end
 
       it 'succeeds if importer succeeds' do
@@ -296,22 +297,5 @@ RSpec.describe Projects::ImportService do
         subject.execute
       end
     end
-
-    def stub_github_omniauth_provider
-      provider = ActiveSupport::InheritableOptions.new(
-        'name' => 'github',
-        'app_id' => 'asd123',
-        'app_secret' => 'asd123',
-        'args' => {
-          'client_options' => {
-            'site' => 'https://github.com/api/v3',
-            'authorize_url' => 'https://github.com/login/oauth/authorize',
-            'token_url' => 'https://github.com/login/oauth/access_token'
-          }
-        }
-      )
-
-      stub_omniauth_setting(providers: [provider])
-    end
   end
 end