identity: Clarify validity period for auth keys.

The AIDL said "one year in the future (365 days)" which is not a
constant amount of time given that leap years and leap seconds may
exist. Change this to be a constant amount of seconds instead.

Bug: 271948315
Test: atest VtsHalIdentityTargetTest
Change-Id: I324a809900feb898d2343e02066f2fb237a46e86
diff --git a/identity/aidl/android/hardware/identity/IIdentityCredential.aidl b/identity/aidl/android/hardware/identity/IIdentityCredential.aidl
index abdb00b..df8e2bd 100644
--- a/identity/aidl/android/hardware/identity/IIdentityCredential.aidl
+++ b/identity/aidl/android/hardware/identity/IIdentityCredential.aidl
@@ -370,7 +370,8 @@
      *  - issuer: CN shall be set to "Android Identity Credential Key". (fixed value:
      *    same on all certs)
      *
-     *  - validity: should be from current time and one year in the future (365 days).
+     *  - validity: should be from current time and 31536000 seconds in the
+     *    future (approximately 365 days).
      *
      *  - subjectPublicKeyInfo: must contain attested public key.
      *