authsecret: remove factoryReset()

Factory reset will be handled by each device from recovery or in the
bootloader in response to `fastboot -w`. The requirements of the factory
reset are made explicit. As a result, VTS tests are moving to a host
side test that can factory reset between each test case.

Also clarifies when the remaining method is called.

Test: AuthSecretHidlTest
Bug: 71527305
Change-Id: I9a29568e022eb83061d8db68e1e7971fc53bd823
diff --git a/authsecret/1.0/default/AuthSecret.cpp b/authsecret/1.0/default/AuthSecret.cpp
index 46a3ec1..f9271e9 100644
--- a/authsecret/1.0/default/AuthSecret.cpp
+++ b/authsecret/1.0/default/AuthSecret.cpp
@@ -29,16 +29,12 @@
     return Void();
 }
 
-Return<void> AuthSecret::factoryReset() {
-    // Clear all dependency on the secret.
-    //
-    // With the example of updating a security module, the stored value must be
-    // cleared so that the new primary user enrolled as the approver of updates.
-    //
-    // This implementation does nothing as there is no dependence on the secret.
-
-    return Void();
-}
+// Note: on factory reset, clear all dependency on the secret.
+//
+// With the example of updating a security module, the stored value must be
+// cleared so that the new primary user enrolled as the approver of updates.
+//
+// This implementation does nothing as there is no dependence on the secret.
 
 }  // namespace implementation
 }  // namespace V1_0