Use body_as_json directly instead of via local var assignment (#31696)

spec/requests/well_known/webfinger_spec.rb

@@ -129,9 +129,11 @@ describe 'The /.well-known/webfinger endpoint' do
     end
 
     it 'returns links for the internal account' do
-      json = body_as_json
-      expect(json[:subject]).to eq 'acct:mastodon.internal@cb6e6126.ngrok.io'
-      expect(json[:aliases]).to eq ['https://cb6e6126.ngrok.io/actor']
+      expect(body_as_json)
+        .to include(
+          subject: 'acct:mastodon.internal@cb6e6126.ngrok.io',
+          aliases: ['https://cb6e6126.ngrok.io/actor']
+        )
     end
   end