docs: drop the last reference to the removed constant

backend/tests/preserve_on_behalf_of.rs

@@ -452,7 +452,7 @@ async fn test_preserve_on_behalf_of(db: Pool<Postgres>) -> anyhow::Result<()> {
     assert_eq!(
         returned["policy"]["on_behalf_of_email"].as_str(),
         Some("original@windmill.dev"),
-        "the app response derives the address from the principal"
+        "the response returns the address written through from the principal"
     );
 
     // ========================================

backend/windmill-api/src/apps.rs

@@ -322,9 +322,9 @@ pub struct Policy {
     /// The address `on_behalf_of` resolves to. Every write stores what the principal resolves
     /// to, so it is not taken from the request except when a client names only the address —
     /// which is how a cross-workspace deploy carries an identity — and it is rejected when the
-    /// two disagree. Optional on read: a policy without it executes by deriving from the
-    /// principal, which is what makes removing it a change of default (`MIN_VERSION_DERIVES_
-    /// APP_POLICY_EMAIL`, `docs/app-policy-email-removal.md`).
+    /// two disagree. Optional: a policy without it executes by deriving from the principal, so
+    /// removing it is a change of default rather than of behavior — see
+    /// `docs/app-policy-email-removal.md`.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub on_behalf_of_email: Option<String>,
     //paths: