Reduce Apdex SLI priority for vulnerabilities

The vulnerability management REST APIs are going to be deprecated soon https://gitlab.com/groups/gitlab-org/-/epics/5118

ee/lib/api/vulnerabilities.rb

@@ -6,6 +6,7 @@ module API
     include PaginationParams
 
     feature_category :vulnerability_management
+    urgency :low
 
     helpers ::API::Helpers::VulnerabilitiesHelpers
 

ee/lib/api/vulnerability_findings.rb

@@ -6,6 +6,7 @@ module API
     include ::Gitlab::Utils::StrongMemoize
 
     feature_category :vulnerability_management
+    urgency :low
 
     helpers do
       def pipeline