Fix the `WebHookPostSerializer` spec.

Fix the WebHookPostSerializer spec.

400f79cffcb8819400884b83685bcac2b3057833

diff --git a/spec/serializers/web_hook_post_serializer_spec.rb b/spec/serializers/web_hook_post_serializer_spec.rb
index c844fda4b7..790a13269b 100644
--- a/spec/serializers/web_hook_post_serializer_spec.rb
+++ b/spec/serializers/web_hook_post_serializer_spec.rb
@@ -12,7 +12,7 @@ RSpec.describe WebHookPostSerializer do
 
   it 'should only include the required keys' do
     count = serialized_for_user(admin).keys.count
-    difference = count - 38
+    difference = count - 39
 
     expect(difference).to eq(0), lambda {
       message = +""

GitHub sha: 15c2755b