Modify rule S6721: Fix description (#4535)

* Fix secret_type being undefined

* Remove Workflow for Teams description, as it is not detected by us

* Add missing empty line

rules/S6721/secrets/rule.adoc

@@ -6,12 +6,9 @@ include::../../../shared_content/secrets/rationale.adoc[]
 
 === What is the potential impact?
 
-Teams Workflow webhook URLs have different effects depending on their
-permissions: They can be used only to write Teams posts or to trigger other
-workflows.
+Below are some real-world scenarios that illustrate the potential impact of an attacker exploiting this secret.
 
-Below are some real-world scenarios that illustrate some impacts of an attacker
-exploiting the secret.
+:secret_type: webhook
 
 include::../../../shared_content/secrets/impact/phishing.adoc[]