Merge pull request #2155 from w3c/safetynetdeprecate

Mark Android SafetyNet attestation as deprecated.

index.bs

@@ -6659,6 +6659,8 @@ data</dfn> is identified by the OID `1.3.6.1.4.1.11129.2.1.17`, and its schema i
 
 ## Android SafetyNet Attestation Statement Format ## {#sctn-android-safetynet-attestation}
 
+Note: This format is deprecated and is expected to be removed in a future revision of this document.
+
 When the [=authenticator=] is a [=platform authenticator=] on certain Android platforms, the attestation
 statement may be based on the [SafetyNet API](https://developer.android.com/training/safetynet/attestation#compat-check-response). In
 this case the [=authenticator data=] is completely controlled by the caller of the SafetyNet API (typically an application