chore(pla-1906): update message status condition docs to mention retention enforcement

Author: bceskavich

content/designing-workflows/step-conditions.mdx

@@ -45,6 +45,8 @@ Message status conditions allow you to build a check for one workflow step that
 - An asserting (`"has"`) or negating (`"has not"`) condition operator.
 - The expected delivery or engagement status case.
 
+Message state used to evaluate status conditions is subject to the Knock data retention policy. If you attempt to evaluate a status condition against a message that has expired out of your account's retention window, the condition will always evaluate to a false result. For more information, see our [data retention docs](/manage-your-account/data-retention).
+
 ### Status cases
 
 <Callout