Sanitize link markup for vulnerability chat messages

Changelog: security
EE: true

ee/app/models/integrations/chat_message/vulnerability_message.rb

@@ -19,7 +19,7 @@ module Integrations
 
       def attachments
         [{
-          title: title,
+          title: strip_markup(title),
           title_link: vulnerability_url,
           color: attachment_color,
           fields: attachment_fields

ee/spec/models/integrations/chat_message/vulnerability_message_spec.rb

@@ -31,6 +31,8 @@ RSpec.describe Integrations::ChatMessage::VulnerabilityMessage do
     }
   end
 
+  it_behaves_like Integrations::ChatMessage
+
   describe '#message' do
     it 'returns the correct message' do
       expect(subject.message).to eq("Vulnerability detected in [Foobar Project](https://git.example.com/random/foobar)")