Fix account URI in UpdatePollSerializer (#11194)

* Fix account URI in UpdatePollSerializer

Fixes #11185

* Add specs

spec/serializers/activitypub/update_poll_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ActivityPub::UpdatePollSerializer do
+  let(:account) { Fabricate(:account) }
+  let(:poll)    { Fabricate(:poll, account: account) }
+  let!(:status) { Fabricate(:status, account: account, poll: poll) }
+
+  before(:each) do
+    @serialization = ActiveModelSerializers::SerializableResource.new(status, serializer: ActivityPub::UpdatePollSerializer, adapter: ActivityPub::Adapter)
+  end
+
+  subject { JSON.parse(@serialization.to_json) }
+
+  it 'has a Update type' do
+    expect(subject['type']).to eql('Update')
+  end
+
+  it 'has an object with Question type' do
+    expect(subject['object']['type']).to eql('Question')
+  end
+
+  it 'has the correct actor URI set' do
+    expect(subject['actor']).to eql(ActivityPub::TagManager.instance.uri_for(account))
+  end
+end