Update the comment for generateChallenge

Bug: 182005958
Test: none
Change-Id: Id8c08929a550a93f13d1579b6d2d9745db3001d1
diff --git a/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl b/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl
index 7502515..f9c13e6 100644
--- a/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl
+++ b/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl
@@ -69,7 +69,7 @@
      *
      * Note that this interface allows multiple in-flight challenges. Invoking generateChallenge
      * twice does not invalidate the first challenge. The challenge is invalidated only when:
-     *   1) Its lifespan exceeds the HAL's internal challenge timeout
+     *   1) Its lifespan exceeds the challenge timeout defined in the TEE.
      *   2) IFingerprint#revokeChallenge is invoked
      *
      * For example, the following is a possible table of valid challenges: