Deprecate /_matrix/identity/v2

Signed-off-by: Aaron Raimist <aaron@raim.ist>

proposals/2499-client-well-known-fixes.md

@@ -21,5 +21,8 @@ This is consistent with the Server-Server API.
 `/_matrix/identity/versions` API to validate the identity server rather than the deprecated
 `/_matrix/identity/api/v1`.
 
+1. Mark the `/_matrix/identity/v2` status check API as deprecated. `/_matrix/identity/versions`
+is the suggested replacement.
+
 1. The maximum size of size of the well-known file is 51200 bytes. A client or server
 requesting a well-known file MUST abort and FAIL_PROMPT if the response exceeds 51200 bytes.